Teleportation is the hypothetical transfer of matter or energy from one point to another without traversing the physical space between them. It is a common subject in science fiction and fantasy literature. Teleportation is often paired with time travel, being that the traveling between the two points takes an unknown period of time, sometimes being immediate. An apport is a similar phenomenon featured in parapsychology and spiritualism.
The use of the term teleport to describe the hypotheticalmovement
of material objects between one place and another without physically
traversing the distance between them has been documented as early as
1878.
American writer Charles Fort is credited with having coined the word teleportation in 1931 to describe the strange disappearances and appearances of anomalies, which he suggested may be connected. As in the earlier usage, he joined the Greek prefix tele- (meaning "remote") to the root of the Latin verb portare (meaning "to carry"). Fort's first formal use of the word occurred in the second chapter of his 1931 book Lo!:
Mostly in this book I shall specialize upon indications that there exists a transportory force that I shall call Teleportation.
I shall be accused of having assembled lies, yarns, hoaxes, and
superstitions. To some degree I think so, myself. To some degree, I do
not. I offer the data.
Teleportation is a common subject in science fiction literature,
film, video games, and television. The use of matter transmitters in
science fiction originated at least as early as the 19th century. An early example of scientific teleportation (as opposed to magical or spiritual teleportation) is found in the 1897 novel To Venus in Five Seconds by Fred T. Jane. Jane's protagonist is transported from a strange-machinery-containing gazebo on Earth to planet Venus – hence the title.
The earliest recorded story of a "matter transmitter" was Edward Page Mitchell's "The Man Without a Body" in 1877.
Live performance
Teleportation illusions have featured in live performances throughout
history, often under the fiction of miracles, psychic phenomenon, or
magic. The cups and balls trick has been performed since 3 BC and can involve balls vanishing, reappearing, teleporting and
transposing (objects in two locations interchanging places). A common
trick of close-up magic
is the apparent teleportation of a small object, such as a marked
playing card, which can involve sleight-of-hand, misdirection, and
pickpocketing. Magic shows were popular entertainments at fairs in the 18th century and moved into permanent theatres in the mid-19th century. Theatres provided greater control of the environment and viewing angles for more elaborate illusions,
and teleportation tricks grew in scale and ambition. To increase
audience excitement, the teleportation illusion could be conducted under
the theme of a predicament escape. Magic shows achieved widespread success during the Golden Age of Magic in the late 19th and early 20th centuries.
Quantum teleportation is distinct from regular teleportation, as it does not transfer matter from one place to another, but rather transmits the quantum information necessary to prepare a (microscopic) target system in the same quantum state
as the source system. The scheme was named quantum "teleportation",
because certain properties of the source system are recreated in the
target system without any apparent quantum information carrier propagating between the two.
In 1993, Bennett et al proposed that a quantum state of a particle could be transferred to
another distant particle, without moving the two particles at all. This
is called quantum state teleportation. There are many following
theoretical and experimental papers published.
In 2014, researcher Ronald Hanson
and colleagues from the Technical University Delft in the Netherlands,
demonstrated the teleportation of information between two entangled
quantumbits three metres apart.
A generalization of quantum mechanics suggests particles could be teleported from one place to another. This is called particle teleportation. With this concept, superconductivity can be viewed as the teleportation of some electrons in the superconductor and superfluidity
as the teleportation of some of the atoms in the cellular tube. Further
analysis shows that the teleportation time increases with the square
root of mass and longer teleportation times require sustained quantum
coherence. While particle teleportation may be feasible for an electron,
a proton may not be feasible.
The evolution of the brain is the progressive development and complexity of neural structures
over millions of years, resulting in the diverse range of brain sizes
and functions observed across different species today, particularly in vertebrates.
The evolution of the brain
has exhibited diverging adaptations within taxonomic classes, such as
Mammalia, and even more diverse adaptations across other taxonomic
classes. Brain-to-body size scales allometrically. This means that as body size changes, so do other physiological,
anatomical, and biochemical connections between the brain and body. Small-bodied mammals tend to have relatively large brains compared to
their bodies, while larger mammals (such as whales) have smaller
brain-to-body ratios. When brain weight is plotted against body weight
for primates, the regression line of the sample points can indicate the
brain power of a species. For example, lemurs fall below this line,
suggesting that for a primate of their size, a larger brain would be
expected. In contrast, humans lie well above this line, indicating they
are more encephalized than lemurs and, in fact, more encephalized than any other primate. This suggests that human brains have undergone a larger evolutionary
increase in complexity relative to size. Some of these changes have been
linked to multiple genetic factors, including proteins and other
organelles.
One approach to understanding overall brain evolution is to use a paleoarchaeological
timeline to trace the necessity for ever-increasing complexity in
structures that allow for chemical and electrical signaling. Because
brains and other soft tissues do not fossilize as readily as mineralized tissues,
scientists often look to other structures as evidence in the fossil
record to get an understanding of brain evolution. This, however, leads
to a dilemma as the emergence of organisms with more complex nervous
systems with protective bone or other protective tissues that can then
readily fossilize occur in the fossil record before evidence for
chemical and electrical signaling. Evidence from 2008 showed that the ability to transmit electrical and
chemical signals existed even before more complex multicellular
lifeforms.
Fossilization of brain tissue, as well as other soft tissue, is
nonetheless possible, and scientists can infer that the first brain
structure appeared at least 521 million years ago, with fossil brain
tissue present in sites of exceptional preservation.
Another approach to understanding brain evolution is to look at
extant organisms that do not possess complex nervous systems, comparing
anatomical features that allow for chemical or electrical messaging. For
example, choanoflagellates are organisms that possess various membrane channels that are crucial to electrical signaling. The membrane channels of choanoflagellates' are homologous
to the ones found in animal cells, and this is supported by the
evolutionary connection between early choanoflagellates and the
ancestors of animals. Another example of extant organisms with the capacity to transmit electrical signals would be the glass sponge, a multicellular organism, which is capable of propagating electrical impulses without the presence of a nervous system.
Before the evolutionary development of the brain, nerve nets, the simplest form of a nervous system developed. These nerve nets were a sort of precursor for the more evolutionarily advanced brains. They were first observed in Cnidaria
and consist of a number of neurons spread apart that allow the organism
to respond to physical contact. They are able to rudimentarily detect
food and other chemicals, but these nerve nets do not allow them to
detect the source of the stimulus.
Ctenophores
also demonstrate this crude precursor to a brain or centralized nervous
system, however they phylogenetically diverged before the phylum Porifera
(the Sponges) and Cnidaria. There are two current theories on the
emergence of nerve nets. One theory is that nerve nets may have
developed independently in Ctenophores and Cnidarians. The other theory
states that a common ancestor may have developed nerve nets, but they
were lost in Porifera. While comparing the average neuron size and the
packing density the difference between primate and mammal brains is
shown.
A trend in brain evolution according to a study done with mice,
chickens, monkeys and apes concluded that more evolved species tend to
preserve the structures responsible for basic behaviors. A long term
human study comparing the human brain to the primitive brain found that
the modern human brain contains the primitive hindbrain region – what
most neuroscientists call the protoreptilian brain.
The purpose of this part of the brain is to sustain fundamental
homeostatic functions, which are self regulating processes organisms use
to help their bodies adapt. The pons and medulla
are major structures found there. A new region of the brain developed
in mammals about 250 million years after the appearance of the
hindbrain. This region is known as the paleomammalian brain, the major
parts of which are the hippocampi and amygdalas, often referred to as the limbic system.
The limbic system deals with more complex functions including
emotional, sexual and fighting behaviors. Of course, animals that are
not vertebrates also have brains, and their brains have undergone separate evolutionary histories.
The brainstem and limbic system are largely based on nuclei, which are essentially balled-up clusters of tightly packed neurons and the axon fibers that connect them to each other, as well as to neurons in other locations. The other two major brain areas (the cerebrum and cerebellum) are based on a cortical
architecture. At the outer periphery of the cortex, the neurons are
arranged into layers (the number of which vary according to species and
function) a few millimeters thick. There are axons that travel between
the layers, but the majority of axon mass is below the neurons
themselves. Since cortical neurons and most of their axon fiber tracts
do not have to compete for space, cortical structures can scale more
easily than nuclear ones. A key feature of cortex is that because it
scales with surface area, more of it can be fit inside a skull by
introducing convolutions, in much the same way that a dinner napkin can
be stuffed into a glass by wadding it up. The degree of convolution is
generally greater in species with more complex behavior, which benefits
from the increased surface area.
The cerebellum, or "little brain," is behind the brainstem and below the occipital lobe of the cerebrum
in humans. Its purposes include the coordination of fine sensorimotor
tasks, and it may be involved in some cognitive functions, such as
language and different motor skills that may involve hands and feet. The
cerebellum helps keep equilibrium. Damage to the cerebellum would
result in all physical roles in life to be affected. Human cerebellar
cortex is finely convoluted, much more so than cerebral cortex. Its
interior axon fiber tracts are called the arbor vitae, or Tree of Life.
The area of the brain with the greatest amount of recent evolutionary change is called the neocortex. In reptiles and fish, this area is called the pallium
and is smaller and simpler relative to body mass than what is found in
mammals. According to research, the cerebrum first developed about 200
million years ago. It is responsible for higher cognitive functions—for
example, language, thinking, and related forms of information
processing. It is also responsible for processing sensory input (together with the thalamus,
a part of the limbic system that acts as an information router). The
thalamus receives the different sensations before the information is
then passed onto the cerebral cortex. Most of its function is subconscious,
that is, not available for inspection or intervention by the conscious
mind. The neocortex is an elaboration, or outgrowth, of structures in
the limbic system, with which it is tightly integrated. The neocortex is
the main part controlling many brain functions as it covers half of the
whole brain in volume. The development of these recent evolutionary
changes in the neocortex likely occurred as a result of new neural
network formations and positive selections of certain genetic
components.
In addition to studying the fossil record, evolutionary history can be investigated via embryology. An embryo
is an unborn/unhatched animal and evolutionary history can be studied
by observing how processes in embryonic development are conserved (or
not conserved) across species. Similarities between different species
may indicate evolutionary connection. One way anthropologists study
evolutionary connection between species is by observing orthologs. An
ortholog is defined as two or more homologous genes between species that
are evolutionarily related by linear descent. By using embryology the
evolution of the brain can be tracked between various species.
Bone morphogenetic protein (BMP), a growth factor that plays a significant role in embryonic neural development, is highly conserved amongst vertebrates, as is sonic hedgehog
(SHH), a morphogen that inhibits BMP to allow neural crest development.
Tracking these growth factors with the use of embryology provides a
deeper understanding of what areas of the brain diverged in their
evolution. Varying levels of these growth factors lead to differing
embryonic neural development which then in turn affects the complexity
of future neural systems. Studying the brain's development at various
embryonic stages across differing species provides additional insight
into what evolutionary changes may have historically occurred. This then
allows scientists to look into what factors may have caused such
changes, such as links to neural network diversity, growth factor
production, protein- coding selections, and other genetic factors.
Randomizing access and increasing size
Some animal phyla have gone through major brain enlargement through evolution (e.g. vertebrates and cephalopods
both contain many lineages in which brains have grown through
evolution) but most animal groups are composed only of species with
extremely small brains. Some scientists argue that this difference is due to vertebrate and cephalopod neurons
having evolved ways of communicating that overcome the scalability
problem of neural networks
while most animal groups have not. They argue that traditional neural
networks fail to improve their function when scaled up because filtering
based on previously known probabilities creates self-fulfilling prophecy-like
biases. These biases generate false statistical evidence, producing a
completely inaccurate worldview. In contrast, randomized access can
overcome this problem, allowing brains to scale to more discriminating conditioned reflexes. This, in turn, can lead to new worldview-forming abilities
once certain thresholds are reached. This means when neurons scale in a
non randomized fashion that their functionality becomes more limited
due to their neural networks being unable to process more complex
systems without the exposure to new formations. This is explained by
randomization allowing the entire brain to eventually get access to all
information over the course of many shifts even though instant privileged access is physically impossible. They cite that vertebrate neurons transmit virus-like capsules containing RNA
that are sometimes read in the neuron to which it is transmitted and
sometimes passed further on unread which creates randomized access, and
that cephalopod neurons make different proteins from the same gene which
suggests another mechanism for randomization of concentrated
information in neurons, both making it evolutionarily worth scaling up
brains.
Brain re-organization
With the use of in vivo Magnetic resonance imaging (MRI)
and tissue sampling, different cortical samples from members of each
hominoid species were analyzed. In each species, specific areas were
either relatively enlarged or shrunken, which can detail neural
organizations. Different sizes in the cortical areas can show specific
adaptations, functional specializations and evolutionary events that
were changes in how the hominoid brain is organized. In early
prediction it was thought that the frontal lobe, a large part of the
brain that is generally devoted to behavior and social interaction,
predicted the differences in behavior between hominoid and humans.
Discrediting this theory was evidence supporting that damage to the
frontal lobe in both humans and hominoids show atypical social and
emotional behavior; thus, this similarity means that the frontal lobe
was not very likely to be selected for reorganization. Instead, it is
now believed that evolution occurred in other parts of the brain that
are strictly associated with certain behaviors. The reorganization that
took place is thought to have been more organizational than volumetric;
whereas the brain volumes were relatively the same but specific
landmark position of surface anatomical features, for example, the
lunate sulcus suggest that the brains had been through a neurological
reorganization. There is also evidence that the early hominin lineage also underwent a
quiescent period, or a period of dormancy, which supports the idea of
neural reorganization.
Dental fossil records for early humans and hominins show that immature hominins, including australopithecines and members of Homo,
have a quiescent period (Bown et al. 1987). A quiescent period is a
period in which there are no dental eruptions of adult teeth; at this
time the child becomes more accustomed to social structure, and
development of culture. During this time the child is given an extra
advantage over other hominoids, devoting several years into developing
speech and learning to cooperate within a community. This period is also discussed in relation to encephalization. It was
discovered that chimpanzees do not have this neutral dental period,
which suggests that a quiescent period occurred in very early hominin
evolution. Using the models for neurological reorganization it can be
suggested the cause for this period, dubbed middle childhood, is most
likely for enhanced foraging abilities in varying seasonal environments.
Genetic factors in recent evolution
Genes involved in the neuro-development and in neuron physiology are
extremely conserved between mammalian species (94% of genes expressed in
common between humans and chimpanzees, 75% between humans and mice),
compared to other organs. Therefore, few genes account for species
differences in the human brain development and function.
Development of the human cerebral cortex
Main differences rely on the evolution of non-coding genomic regions,
involved in the regulation of gene expression. This leads to
differential expression of genes during the development of the human
brain compared to other species, including chimpanzees. Some of these
regions evolved fast in the human genome (human accelerated regions). The new genes expressed during human neurogenesis are notably associated with the NOTCH, WNT and mTOR pathways, but are also involved ZEB2, PDGFD and its receptor PDGFRβ. The human cerebral cortex is also characterized by a higher gradient of retinoic acid in the prefrontal cortex, leading to higher prefrontal cortex volume. All these differential gene expression lead to higher proliferation of the neural progenitors
leading to more neurons in the human cerebral cortex. Some genes are
lost in their expression during the development of the human cerebral
cortex like GADD45G and FLRT2/FLRT3.
Another source of molecular novelty rely on new genes in the human or hominid
genomes through segmental duplication. Around 30 new genes in the
hominid genomes are dynamically expressed during human corticogenesis.
Some were linked to higher proliferation of neural progenitors: NOTCH2NLA/B/C, ARHGAP11B, CROCCP2, TBC1D3, TMEM14B. Patients with deletions with NOTCH2NL genes display microcephaly, showing the necessity of such duplicated genes, acquired in the human genomes, in the proper corticogenesis.
MCPH1 and ASPM
Bruce Lahn, the senior author at the Howard Hughes Medical Center at
the University of Chicago and colleagues have suggested that there are
specific genes that control the size of the human brain. These genes
continue to play a role in brain evolution, implying that the brain is
continuing to evolve. The study began with the researchers assessing 214
genes that are involved in brain development. These genes were obtained
from humans, macaques, rats and mice. Lahn and the other researchers
noted points in the DNA sequences that caused protein alterations. These
DNA changes were then scaled to the evolutionary time that it took for
those changes to occur. The data showed the genes in the human brain
evolved much faster than those of the other species. Once this genomic
evidence was acquired, Lahn and his team decided to find the specific
gene or genes that allowed for or even controlled this rapid evolution.
Two genes were found to control the size of the human brain as it
develops. These genes are Microcephalin (MCPH1) and Abnormal Spindle-like Microcephaly (ASPM).
The researchers at the University of Chicago were able to determine
that under the pressures of selection, both of these genes showed
significant DNA sequence changes. Lahn's earlier studies displayed that
Microcephalin experienced rapid evolution along the primate lineage
which eventually led to the emergence of Homo sapiens. After the
emergence of humans, Microcephalin seems to have shown a slower
evolution rate. On the contrary, ASPM showed its most rapid evolution
in the later years of human evolution once the divergence between
chimpanzees and humans had already occurred.
Each of the gene sequences went through specific changes that led
to the evolution of humans from ancestral relatives. In order to
determine these alterations, Lahn and his colleagues used DNA sequences
from multiple primates then compared and contrasted the sequences with
those of humans. Following this step, the researchers statistically
analyzed the key differences between the primate and human DNA to come
to the conclusion, that the differences were due to natural selection.
The changes in DNA sequences of these genes accumulated to bring about a
competitive advantage and higher fitness that humans possess in
relation to other primates. This comparative advantage is coupled with a
larger brain size which ultimately allows the human mind to have a
higher cognitive awareness.
ZEB2 protein
ZEB2
ZEB2 is a protein- coding gene in the Homo sapien species. A 2021 study found that a delayed change in the shape of early brain cells causes the distinctly large human forebrain compared to other apes and identify ZEB2 as a genetic regulator of it, whose manipulation lead to acquisition of nonhuman ape cortical architecture in brain organoids.
NOVA1
In 2021, researchers reported that brain organoids created with stem cells into which they reintroduced the archaic gene variant NOVA1 present in Neanderthals and Denisovans via CRISPR-Cas9 shows that it has a major impact on neurodevelopment and that such genetic mutations during the evolution of the human brain underlie traits that separate modern humans from extinct Homo
species. They found that expression of the archaic NOVA1 in cortical
organoids leads to "modified synaptic protein interactions, affects glutamatergic signaling, underlies differences in neuronal connectivity, and promotes higher heterogeneity of neurons regarding their electrophysiological profiles". This research suggests positive selection of the modern NOVA1 gene,
which may have promoted the randomization of neural scaling. A
subsequent study failed to replicate the differences in organoid
morphology between the modern human and the archaic NOVA1 variant, consistent with suspected unwanted side effects of CRISPR editing in the original study.
SRGAP2C and neuronal maturation
Less is known about neuronal maturation. Synaptic gene and protein expression are protracted, in line with the protracted
synaptic maturation of human cortical neurons so called neoteny. This
probably relies on the evolution of non-coding genomic regions. The
consequence of the neoteny could be an extension of the period of synaptic plasticity and therefore of learning. A human-specific duplicated gene, SRGAP2C accounts for this synaptic neoteny and acts by regulating molecular pathways linked to neurodevelopmental disorders. Other genes are deferentially expressed in human neurons during their development such as osteocrin or cerebelin-2.
LRRC37B and neuronal electrical properties
Even less is known about molecular specificities linked to the
physiology of the human neurons. Human neurons are more divergent in the
genes they express compared to chimpanzees than chimpanzees to gorilla,
which suggests an acceleration of non-coding genomic regions associated
with genes involved in neuronal physiology, in particular linked to the
synapses. A hominid-specific duplicated gene, LRRC37B, codes for a transmembrane receptor that is selectively localized at the axon initial segment of human cortical pyramidal neurons. It inhibits their voltage-gated sodium channels that generate the action potentials leading to a lower neuronal excitability. Human cortical pyramidal neurons display a lower excitability compared to other mammalian species (including macaques and marmosets) which could lead to different circuit functions in the human species. Therefore, LRRC37B
whose expression has been acquired in the human lineage after the
separation from the chimpanzees could be a key gene in the function of
the human cerebral cortex. LRRC37B binds to secreted FGF13A and SCN1B and modulate indirectly the activity of SCN8A, all involved in neural disorders such as epilepsy and autism.
Therefore, LRRC37B may contribute to human-specific sensitivities to
such disorders, both involved defects in neuronal excitability.
Genome repair
The genomicDNA of postmitotic neurons ordinarily does not replicate. Protection strategies have evolved to ensure the distinctive longevity of the neuronal genome. Human neurons are reliant on DNA repair
processes to maintain function during an individual's life-time. DNA
repair tends to occur preferentially at evolutionarily conserved sites
that are specifically involved with the regulation of expression of genes essential for neuronal identity and function.
Other factors
Many other genetics may also be involved in recent evolution of the brain.
For instance, scientists showed experimentally, with brain organoids grown from stem cells, how differences between humans and chimpanzees are also substantially caused by non-coding DNA (often discarded as relatively meaningless "junk DNA") – in particular via CRE-regulated expression of the ZNF558 gene for a transcription factor that regulates the SPATA18 gene.SPATA18 gene encodes a protein and is able to influence lysosome-like
organelles that are found within mitochondria that eradicate oxidized
mitochondrial proteins. This helps monitor the quality of the
mitochondria as the disregulation of its quality control has been linked
to cancer and degenerative diseases. This example may contribute to illustrations of the complexity and scope of relatively recent evolution to Homo sapiens.
A change in gene TKTL1 could be a key factor of recent brain evolution and difference of modern humans to (other) apes and Neanderthals, related to neocortex-neurogenesis. However, the "archaic" allele attributed to Neanderthals is present in 0.03% of Homo sapiens, but no resultant phenotypic differences have been reported in these people. Additionally, as Herai et al. contend, more is not always better. In
fact, enhanced neuron production "can lead to an abnormally enlarged
cortex and layer-specific imbalances in glia/neuron ratios and neuronal subpopulations during neurodevelopment." Even the original study's authors agree that "any attempt to discuss
prefrontal cortex and cognitive advantage of modern humans over
Neandertals based on TKTL1 alone is problematic".
Some of the prior study's authors reported a similar ARHGAP11B mutation in 2016.
Epigenetics also play a major role in the brain evolution in and to humans.
Recently evolved traits
Language
A genome-wide association studymeta-analysis reported genetic factors of, the so far uniquely human, language-related capacities, in particular factors of differences in skill-levels of five tested traits. It e.g. identified association with neuroanatomy of a language-related brain area via neuroimaging
correlation. The data contributes to identifying or understanding the
biological basis of this recently evolved characteristic capability.
One of the prominent ways of tracking the evolution of the human
brain is through direct evidence in the form of fossils. The
evolutionary history of the human brain shows primarily a gradually
bigger brain relative to body size during the evolutionary path from
early primates to hominids and finally to Homo sapiens. Because
fossilized brain tissue is rare, a more reliable approach is to observe
anatomical characteristics of the skull that offer insight into brain
characteristics. One such method is to observe the endocranial cast
(also referred to as endocasts).
Endocasts occur when, during the fossilization process, the brain
deteriorates away, leaving a space that is filled by surrounding
sedimentary material over time. These casts, give an imprint of the
lining of the brain cavity, which allows a visualization of what was
there. This approach, however, is limited in regard to what information can be
gathered. Information gleaned from endocasts is primarily limited to
the size of the brain (cranial capacity or endocranial volume), prominent sulci and gyri, and size of dominant lobes or regions of the brain. While endocasts are extremely helpful in revealing superficial brain
anatomy, they cannot reveal brain structure, particularly of deeper
brain areas. By determining scaling metrics of cranial capacity as it
relates to total number of neurons present in primates, it is also
possible to estimate the number of neurons through fossil evidence.
Facial reconstruction of a Homo georgicus from over 1.5 Mya
Despite the limitations to endocasts, they can and do provide a basis
for understanding human brain evolution, which shows primarily a
gradually bigger brain. The evolutionary history of the human brain
shows primarily a gradually bigger brain relative to body size during
the evolutionary path from early primates to hominins and finally to Homo sapiens.
This trend that has led to the present day human brain size indicates
that there has been a 2-3 factor increase in size over the past 3
million years. This can be visualized with current data on hominin evolution, starting with Australopithecus, a group of hominins from which humans are likely descended. After all of the data, all observations concluded that the main
development that occurred during evolution was the increase of brain
size.
However, recent research has called into question the hypothesis of a threefold increase in brain size when comparing Homo sapiens with Australopithecus
and chimpanzees. For example, in an article published in 2022 compiled a
large data set of contemporary humans and found that the smallest human
brains are less than twice that of large brained chimpanzees. As the
authors write '...the upper limit of chimpanzee brain size is 500g/ml
yet numerous modern humans have brain size below 900 g/ml.'[53] (Note that in this quote, the unit g/ml is to be understood not in the usual way as gram per millilitre but rather as gram or
millilitre. This is consistent because brain density is close to 1
g/ml.) Consequently, the authors argue that the notion of an increase in
brain size being related to advances in cognition needs to be
re-thought in light of global variation in brain size, as the brains of
many modern humans with normal cognitive capacities are only 400g/ml
larger than chimpanzees. Additionally, much of the increase in brain
size - which occurs to a much greater degree in specific modern
populations - can be explained by increases in correlated body size
related to diet and climatic factors.
Australopiths
lived from 3.85 to 2.95 million years ago with the general cranial
capacity somewhere near that of the extant chimpanzee—around 300–500 cm3. Considering that the volume of the modern human brain is around 1,352 cm3 on average this represents a substantial amount of brain mass evolved. Australopiths are estimated to have a total neuron count of ~30-35 billion.
Progressing along the human ancestral timeline, brain size continues to steadily increase (see Homininae) when moving into the era of Homo. For example, Homo habilis, living 2.4 million to 1.4 million years ago and argued to be the first Homo species based on a host of characteristics, had a cranial capacity of around 600 cm3. Homo habilis is estimated to have had ~40 billion neurons.
A little closer to present day, Homo heidelbergensis lived from around 700,000 to 200,000 years ago and had a cranial capacity of around 1290 cm3 and having around 76 billion neurons.
Homo neaderthalensis, living 400,000 to 40,000 years ago, had a cranial capacity comparable to that of modern humans at around 1500–1600 cm3on average, with some specimens of Neanderthal having even greater cranial capacity. Neanderthals are estimated to have had around 85 billion neurons. The increase in brain size topped with Neanderthals, possibly due to their larger visual systems.
It is also important to note that the measure of brain mass or volume, seen as cranial capacity, or even relative brain size,
which is brain mass that is expressed as a percentage of body mass, are
not a measure of intelligence, use, or function of regions of the
brain. Total neurons, however, also do not indicate a higher ranking in
cognitive abilities. Elephants have a higher number of total neurons
(257 billion) compared to humans (100 billion). Relative brain size, overall mass, and total number of neurons are only
a few metrics that help scientists follow the evolutionary trend of
increased brain to body ratio through the hominin phylogeny.
In 2021, scientists suggested that the brains of early Homo from Africa and Dmanisi, Georgia, Western Asia "retained a great ape-like structure of the frontal lobe" for far longer than previously thought – until about 1.5 million years ago. Their findings imply that Homofirst dispersed out of Africa
before human brains evolved to roughly their modern anatomical
structure in terms of the location and organization of individual brain
regions. It also suggests that this evolution occurred – not during –
but only long after the Homo lineage evolved ~2.5 million years ago and
after they – Homo erectus in particular – evolved to walk upright. What is the least controversial is that the brain expansion started about 2.6 Ma (about the same as the start of the Pleistocene), and ended around 0.2 Ma.
In
addition to just the size of the brain, scientists have observed
changes in the folding of the brain, as well as in the thickness of the cortex.
The more convoluted the surface of the brain is, the greater the
surface area of the cortex which allows for an expansion of cortex. It
is the most evolutionarily advanced part of the brain. Greater surface area of the brain is linked to higher intelligence as
is the thicker cortex but there is an inverse relationship—the thicker
the cortex, the more difficult it is for it to fold. In adult humans,
thicker cerebral cortex has been linked to higher intelligence.
The neocortex is the most advanced and most evolutionarily young
part of the human brain. It is six layers thick and is only present in
mammals. It is especially prominent in humans and is the location of
most higher level functioning and cognitive ability. The six-layered neocortex found in mammals is evolutionarily derived from a three-layer cortex present in all modern reptiles. This three-layer cortex is still conserved in some parts of the human
brain such as the hippocampus and is believed to have evolved in mammals
to the neocortex during the transition between the Triassic and
Jurassic periods. After looking at history, the mammals had little neocortex compared to the primates as they had more cortex. The three layers of this reptilian cortex correlate strongly to the first, fifth and sixth layers of the mammalian neocortex. Across species of mammals, primates have greater neuronal density
compared to rodents of similar brain mass and this may account for
increased intelligence.
Theories of human brain evolution
Explanations of the rapid evolution and exceptional size of the human
brain can be classified into five groups: instrumental, social,
environmental, dietary, and anatomo-physiological. The instrumental
hypotheses are based on the logic that evolutionary selection for larger brains is beneficial for species survival, dominance, and spread, because larger brains facilitate food-finding and mating success. The social hypotheses suggest that social behavior stimulates evolutionary expansion of brain size. Similarly, the environmental hypotheses suppose that encephalization is promoted by environmental factors such as stress, variability, and consistency. The dietary hypotheses maintain that food quality and certain
nutritional components directly contributed to the brain growth in the Homo genus. The anatomo-physiologic concepts, such as cranio-cerebral vascular hypertension due to head-down posture of the anthropoid fetus during pregnancy, are primarily focused on anatomic-functional changes that predispose to brain enlargement.
No single theory can completely account for human brain
evolution. Multiple selective pressures in combination seems to have
been involved. Synthetic theories have been proposed, but have not clearly explained reasons for the uniqueness of the human
brain. Puzzlingly, brain enlargement has been found to have occurred
independently in different primate lineages, but only human lineage ended up with an exceptional brain capacity. Fetal head-down posture may be an explanation of this conundrum because Homo sapiens is the only primate obligatory biped with upright posture.
Hypothetical technology is technology that does not exist yet, but that could exist in the future. This article presents examples of technologies that have been hypothesized or proposed, but that have not been developed yet. An example of hypothetical technology is teleportation.
Artificial general intelligence (AGI) is a hypothetical artificial intelligence
that demonstrates a human-like ability to learn. AGI is a machine which
could do all human activities with the efficiency of a machine. It is a
primary goal of artificial intelligence research and a common topic among science fiction writers and futurists. Artificial general intelligence is also referred to as strong AI, full AI or one that has the ability to perform "general intelligent action". AGI is associated with traits such as consciousness, sentience, sapience, and self-awareness, which are observed in living beings.
Whole brain emulation (WBE) or mind uploading (sometimes called mind
copying or mind transfer) is the hypothetical process of copying mental
content (including long-term memory and "self") from a particular brain
substrate and copying it to a computational or storage device, such as a
digital, analog, quantum-based, or software-based artificial neural network. The computational device could then run a simulation
model of the brain information processing, such that it responds in
essentially the same way as the original brain (i.e., indistinguishable
from the brain for all relevant purposes) and experiences having a consciousmind.
Mind uploading may potentially be accomplished by at least two
methods: Copy-and-Transfer or Gradual Replacement of neurons. In the
former method, mind uploading would be achieved by scanning and mapping
the salient features of a biological brain, and then by copying,
transferring and storing that information state into a computer system
or another computational device. The simulated mind could be within a virtual reality or simulated world,
supported by an anatomic 3D body simulation model. Alternatively, the
simulated mind could reside in a computer that's inside (or connected
to) a humanoidrobot or a biological body.
Space flight
There are many forms of spaceflight that have been proposed that have
not, so far, been developed but are thought to be possible. Some, like
the space elevator are under active development.Others, like Project Orion,
a nuclear bomb propulsion system, are entirely paper exercises. As it
happens, Orion is thought to be entirely achievable with existing
technology (the obstacles to it are environmental and political rather
than technological), whereas the space elevator depends on the development of a material for the cable with a very high specific strength.
A space elevator is a proposed type of space transport system. Its main component is a ribbon-like cable (also called a tether)
starting at or near a planetary surface and extending into space. It is
designed to permit vehicle transport along the cable directly into
space or orbit without the use of large rockets.
An Earth-based space elevator would consist of a cable with one end
attached to the surface near the equator and the other end in space
beyond geostationary orbit
(35,800 km altitude). The competing forces of gravity, which are
stronger at the lower end, and the outward/upward centrifugal force,
which is stronger at the upper end, would result in the cable staying up
under tension, and stationary over a single position on Earth. Once
deployed, the tether would be ascended repeatedly by mechanical means to
orbit, and descended to return to the surface from orbit.
On Earth, with its relatively strong gravity, current technology
is not capable of manufacturing tether materials that are sufficiently strong and light enough to build a space elevator. However, recent concepts for a space elevator are notable for their plans to use carbon nanotube or boron nitride nanotube-based materials as the tensile element in the tether design.
The rotating skyhook, or momentum-exchange tether, is an idea related
to the space elevator concept. It is one of the many proposed
applications of space tethers,
which include some propulsion systems. The tether is rotated from a
heavy orbiting vehicle such that the far end, weighted with a docking
station, periodically enters Earth's atmosphere. With the right timing,
a fast aircraft can transfer cargo and passengers during the brief time
the skyhook is at the bottom of its cycle and stationary relative to
Earth's surface.
A light sail is a proposed propulsion system that uses the momentum
transferred to a sail by light impinging on it. A light sail could use
sunlight to achieve interplanetary travel without carrying large quantities of onboard fuel. Just as a sailboat on Earth can tack into the wind, the light sail can be tacked against the direction of light for a return journey from the outer planets.
At the beginning of the 21st century, light sails were still entirely hypothetical. The Japanese IKAROS spacecraft was launched in 2010 as a proof-of-concept mission for the light sail. It successfully completed a fly-by of Venus using a light sail as its main means of propulsion.
Evolutionary neuroscientists examine changes in genes, anatomy,
physiology, and behavior to study the evolution of changes in the brain. They study a multitude of processes including the evolution of vocal, visual, auditory, taste, and learning systems as well as language evolution and development. In addition, evolutionary neuroscientists study the evolution of specific areas or structures in the brain such as the amygdala, forebrain and cerebellum as well as the motor or visual cortex.
History
Studies of the brain began during ancient Egyptian times but studies
in the field of evolutionary neuroscience began after the publication of
Darwin's On the Origin of Species in 1859. At that time, brain evolution was largely viewed at the time in relation to the incorrect scala naturae.
Phylogeny and the evolution of the brain were still viewed as linear.
During the early 20th century, there were several prevailing theories
about evolution. Darwinism was based on the principles of natural selection and variation, Lamarckism was based on the passing down of acquired traits, Orthogenesis was based on the assumption that tendency towards perfection steers evolution, and Saltationism
argued that discontinuous variation creates new species. Darwin's
became the most accepted and allowed for people to starting thinking
about the way animals and their brains evolve.
The 1936 book The Comparative Anatomy of the Nervous System of Vertebrates Including Man by the Dutch neurologist C.U. Ariëns Kappers (first published in German in 1921) was a landmark publication in the field. Following the Evolutionary Synthesis,
the study of comparative neuroanatomy was conducted with an
evolutionary view, and modern studies incorporate developmental
genetics. It is now accepted that phylogenetic changes occur independently
between species over time and can not be linear. It is also believed
that an increase with brain size correlates with an increase in neural
centers and behavior complexity.
Major arguments
Over time, there are several arguments that would come to define the
history of evolutionary neuroscience. The first is the argument between E.G. St. Hilaire and G. Cuvier over the topic of "common plan versus diversity". St. Hilaire argued that all animals are built based on a single plan or archetype and he stressed the importance of homologies
between organisms, while Cuvier believed that the structure of organs
was determined by their function and that knowledge of the function of
one organ could help discover the functions of other organs.He argued that there were at least four different archetypes. After
Darwin, the idea of evolution was more accepted and St. Hilaire's idea
of homologous structures was more accepted. The second major argument is
that of Aristotle's scala naturae (scale of nature) and the great chain of being versus the phylogenetic bush. The scala naturae,
later also called the phylogenetic scale, was based on the premise that
phylogenies are linear or like a scale while the phylogenetic bush
argument was based on the idea that phylogenies were not linear, and
more resembled a bush – the currently accepted view. A third major
argument dealt with the size of the brain and whether relative size or
absolute size was more relevant in determining function. In the late
18th century, it was determined that brain to body ratio reduces as body
size increases. However more recently, there is more focus on absolute brain size as this scales with internal structures and functions, with the degree of structural complexity, and with the amount of white matter
in the brain, all suggesting that absolute size is much better
predictor of brain function. Finally, a fourth argument is that of
natural selection (Darwinism)
versus developmental constraints (concerted evolution). It is now
accepted that the evolution of development is what causes adult species
to show differences and evolutionary neuroscientists maintain that many
aspects of brain function and structure are conserved across species.
Techniques
Throughout history, we see how evolutionary neuroscience has been dependent on developments in biological theory and techniques. The field of evolutionary neuroscience has been shaped by the
development of new techniques that allow for the discovery and
examination of parts of the nervous system. In 1873, C. Golgi
devised the silver nitrate method which allowed for the description of
the brain at the cellular level as opposed to simply the gross level. Santiago
and Pedro Ramon used this method to analyze numerous parts of brains,
broadening the field of comparative neuroanatomy. In the second half of
the 19th century, new techniques allowed scientists to identify neuronal
cell groups and fiber bundles in brains. In 1885, Vittorio Marchi
discovered a staining technique that let scientists see induced axonal
degeneration in myelinated axons, in 1950, the "original nauta
procedure" allowed for more accurate identification of degenerating
fibers, and in the 1970s, there were several discoveries of multiple
molecular tracers which would be used for experiments even today. In the
last 20 years, cladistics has also become a useful tool for looking at variation in the brain.
Evolution of brains
Many of Earth's early years were filled with brainless creatures, and among them was the amphioxus,
which can be traced as far back as 550 million years ago. Amphioxi had a
significantly simpler way of life, which made it not necessary for them
to have a brain. To replace its absence of a brain, the prehistoric
amphioxi had a limited nervous system,
which was composed of only a bunch of cells. These cells optimized
their uses because many of the cells for sensing intertwined with the
cells used for its very simple system for moving, which allowed it to
propel itself through bodies of water and react without much processing
while the cells remaining were used for the detection of light to
account to the fact that it had no eyes. It also did not need a sense of
hearing. Even though the amphioxi had limited senses, they did not need
them to survive efficiently, as their life was mainly dedicated to
sitting on the seafloor to eat. Although the amphioxus' "brain" might seem severely underdeveloped
compared to their human counterparts, it was set well for its respective
environment, which has allowed it to prosper for millions of years.
Although many scientists once assumed that the brain evolved to
achieve an ability to think, such a view is today considered a great
misconception. 500 million years ago, the Earth entered into the Cambrian
period, where hunting became a new concern for survival in an animal's
environment. At this point, animals became sensitive to the presence of
another, which could serve as food. Although hunting did not inherently
require a brain, it was one of the main steps that pushed the
development of one, as organisms progressed to develop advanced sensory
systems.
In response to progressively complicated surroundings, where
competition between animals with brains started to arise for survival,
animals had to learn to manage their energy. As creatures acquired a variety of senses for perception, animals progressed to develop allostasis,
which played the role of an early brain by forcing the body to gather
past experiences to improve prediction. Since prediction beat reaction,
organisms who planned their manoeuvres were more likely to survive than
those who did not. This came with equally managing energy adequately,
which nature favoured. Animals that had not developed allostasis would
be at a disadvantage for their purpose of exploration, foraging and
reproduction, as death was a higher risk factor.
As allostasis continued to develop in animals, their bodies
equally continuously evolved in size and complexity. They progressively
started to develop cardiovascular systems, respiratory systems and immune systems
to survive in their environments, which required bodies to have
something more complex than the limited quality of cells to regulate
themselves. This encouraged the nervous systems of many creatures to
develop into a brain, which was sizeable and strikingly similar to how
most animal brains look today.
Evolution of the human brain
Darwin, in The Descent of Man,
stipulated that the mind evolved simultaneously with the body.
According to his theory, all humans have a barbaric core that they learn
to deal with. Darwin's theory allowed people to start thinking about the way animals and their brains evolve.
Reptile brain
Plato's insight on the evolution of the human brain contemplated the
idea that all humans were once lizards, with similar survival needs such
as feeding, fighting and mating. In the classical eraPlato first described this concept as the "lizard mind" – the deepest layer and one of three parts of his conception of a three-part human mind. In the 20th century P. MacLean developed a similar, modern triune brain theory.
Recent research in molecular genetics has demonstrated evidence
that there is no difference in the neurons that reptiles and nonhuman
mammals have when compared to humans. Instead, new research speculates
that all mammals, and potentially reptiles, birds and some species of
fish, evolve from a common order pattern. This research reinforces the
idea that human brains are structurally no t any different from many
other organisms.
The cerebral cortex of reptiles resembles that of mammals, although simplified. Although the evolution and function of the human cerebral cortex is
still shrouded in mystery, we know that it is the most dramatically
changed part of the brain during recent evolution. The reptilian brain,
300 million years ago, was made for all our basic urges and instincts
like fighting, reproducing, and mating. The reptile brain evolved
100 million years later and gave us the ability to feel emotion.
Eventually, it was able to develop a rational part that controls our
inner animal.
Visual perception
Vision allows humans to process the world surrounding them to a
certain extent. Through the wavelengths of light, the human brain can
associate them to a specific event. Although the brain obviously
perceives its surroundings at a specific moment, the brain equally
predicts the upcoming changes in the environment. Once it has noticed them, the brain begins to prepare itself to
encounter the new scenario by attempting to develop an adequate
response. This is accomplished by using the data the brain has at its
access, which can be to use past experiences and memories to form a
proper response. However, sometimes the brain fails to predict accurately which means
that the mind perceives a false illustration. Such an incorrect image
occurs when the brain uses an inadequate memory to respond to what it is
facing, which means that the memory does not correlate with the real
scenario.
The rabbit–duck illusion
is a famous ambiguous image in which a rabbit or a duck can be seen.
The earliest known version is an unattributed drawing from the
23 October 1892 issue of Blätter magazine.
Research about how visual perception has developed in evolution is
today best understood through studying present-day primates since the
organization of the brain cannot be ascertained only by analyzing
fossilized skulls.
The brain interprets visual information in the occipital lobe, a
region in the back of the brain. The occipital lobe contains the visual
cortex and the thalamus, which are the two main actors in processing
visual information. The process of interpreting information has proven
to be more complex than "what you see is what you get". Misinterpreting
visual information is more common than previously believed.
As knowledge of the human brain has evolved, researchers discover
that our visual perception is much closer to a construction of the
brain than a direct "photograph" of what is in front of us. This can
lead to misperceiving certain situations or elements in the brain's
attempt to keep us safe. For example, an on-edge soldier believes a
young child with a stick is a grown man with a gun, as the brain's
sympathetic system, or fight-or-flight mode, is activated.
An example of this phenomenon can be observed in the rabbit–duck illusion.
Depending on how the image is looked at, the brain can interpret the
image of a rabbit, or a duck. There is no right or wrong answer, but it
is proof that what is seen may not be the reality of the situation.
Auditory perception
The organization of the human auditory cortex is divided into core,
belt, and parabelt. This closely resembles that of present-day primates.
The concept of auditory perception resembles visual perception
very similarly. Our brain is wired to act on what it expects to
experience. The sense of hearing helps situate an individual, but it
also gives them hints about what else is around them. If something
moves, they know approximately where it is and by the tone of it, the
brain can predict what moved. If someone were to hear leaves rustling in
a forest, the brain might interpret that sound as being an animal which
could be a dangerous factor, but it would simply be another person
walking. The brain can predict many things based on what it is interpreting, however, those predictions may not all be true.
Language development
Evidence of a rich cognitive life in primate relatives of humans is
extensive, and a wide range of specific behaviours in line with
Darwinian theory is well documented. However, until recently, research has disregarded nonhuman primates in
the context of evolutionary linguistics, primarily because unlike vocal
learning birds, our closest relatives seem to lack imitative abilities.
Evolutionary speaking, there is great evidence suggesting a genetic
groundwork for the concept of languages has been in place for millions
of years, as with many other capabilities and behaviours observed today.
While evolutionary linguists agree on the fact that volitional
control over vocalizing and expressing language is a quite recent leap
in the history of the human race, that is not to say auditory perception
is a recent development as well. Research has shown substantial
evidence of well-defined neural pathways linking cortices to organize
auditory perception in the brain. Thus, the issue lies in our abilities
to imitate sounds.
Beyond the fact that primates may be poorly equipped to learn
sounds, studies have shown them to learn and use gestures far better.
Visual cues and motoric pathways developed millions of years earlier in
our evolution, which seems to be one reason for our earlier ability to
understand and use gestures.
Cognitive specializations
Evolution shows how certain environments and surroundings will favor
the development of specific cognitive functions of the brain to aid an
animal or in this case human to successfully live in that environment.
Cognitive specialization in a theory in which cognitive
functions, such as the ability to communicate socially, can be passed
down genetically through offspring. This would benefit species in the
process of natural selection. As for studying this in relation to the
human brain, it has been theorized that very specific social skills
apart from language, such as trust, vulnerability, navigation, and
self-awareness can also be passed by offspring.
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