*- Darwin’s last words in ‘Descent of Man’
*- Process started with single cell some 700 million years
*- 100 trillion cells
*- bipedalism related to culture bearing species
*-lacking the intellectual tools to understand nature, we lack the means to understand ourselves
**- the gap between nature and culture (atoms, genes and memes) will one daybe bridged by one of
our greatest cultural achievements : science.
**- The pivotal event on which human evolution hangs is not arrival of consciousness, ability to talk
or the evolution of big brain but the sudden event of walking on two legs, not four.
*- Most of the characteristics that we envisage uniquely human are actually species specific
amalgams, truly unique recombination or composites of much more modest, pre-existing
increments.
*-The term hominid / hominin is used to separate all bipeds from apes cousins
*- Not all apes that that became bipedal found themselves on a human trajectory. Getting up on two
legs may have rung in a human future for our direct ancestors, but atleast some bipeds, including
some of the ones best known as fossils remained “cranial apes”.
**- what was it about our specific lineage that emancipated the earliest members of our branch
from being just one more type of bipedal ape?
**- the peculiarities of homo sapiens have evolved by fundamettally the same processes that have
determined the peculiarity of other mammals.
*- East Africa has come to be portrayed as the Archetypal Garden of Eden, the centre of the World
of human evlution.
*- Bipedalism adaptation is no different from any other adaptation. It must have been in response to
the dynamics of behaviour, ecology and geography – that drives all evolutionary change.
*- The first bipeds were cranial apes, creatures with ape heads mounted on human like bodies.
*- various explanations for bipedalism.
*-The chimp-human divergence is 7-5mya. The first proven bipedal fossil was dated to around 4.4-
3.5mya – but now a biped fossil has been discovered dated to 6mya.
*- Bipedalism involved changes in the spine, pelvis and head –neck junction and perhaps also the
heels. The feet changed from being claspers to becoming platforms.
*- It was foraging on the ground, in squatting position that demanded these necessary modifications.
*- Bipedalism began before 4.5 mya, even as early as 6mya.
*- Common human-chimp ancestory is dated to some 6-7mya – indicating that bipedalism occurred
immediately after the separation between the two species.
*- Location of this event has been zeroed down to the forests of the eastern African coastal strip
*- Adaptive phase of squat feeding induced re-organization of the trunk that was essential
precondition for balanced standing.
*- The ability to stand without the expenditure of much energy requires good balance. The balance
was missing in the ape ancestor of humans because too much weight was concentrated at the top of
the column and too little stability at the bottom. The quadrupeds were top heavy.
*- Easy non-energic standing requires a downward displacement in the distribution of weight. For
this to happen the upper foreparts should no longer be the largest and the heaviest part of the body.
To achieve such shifts in the distribution of weight in living, functioning bodies there must be
substantial changes in the relative weight of muscles, bones and organs.
*- This change in the eastern African apes came about through ecological and behavioural changes
that rendered exceptionally heavy, powerful forelimbs redundant.
* - single act of standing is inconceivable without such preliminaries (preadaptation)
*- The radical shift in the priority functions of the forelimbs occurred in order to exploit the intensive
and reliable food supply.
*- Hands and arms were meant to turning over leaf litter, selecting, processing and handling foods,
vertical climbing up the trees and also diagonal movement across the trees.
*-as the incidence of bearing weight declined there would come identifiable point at which four
legged movement ceased to be as efficient as simple straightening of the legs. – at this point spine
got balanced vertically.
* - Standing involved reorientation rather than action, a balancing act on a behavioural tightrope.
*- Fossil record provides evidence that bipedal gaits were built on an erect back.
*- Quadrumana – four hands
*-Orgainic bodies respond to numerous challenges such as extremes of temperatures, humidity,
saturation, chemistry, material textures, rays, or waves such as light, noise, vibration or water. The
simplest and most universal responses to such stimuli are simple stop-go or attract-repel action.
*- having the ability to sense and then react to such stimuli has an intimate bearing on the way we
are built as animals, given expressin in that front-end concentration of sensory equipment that we
call a head (origin of cause – effect analysis – intellect).
*- Through it we receive, process and respond to innumerable messages via sophisticated sensory
and neural pathways. We are responding at this most primitive level when we recoil from a blast of
heat or cold, or even from a loud noise or a bad smell.
*- Plants began to flourish on lnad and at water edge at the start of the Devonian 400 mya
*- The major switch from fins to something more like limbs comes with the appearance of the first,
still aquatic, tetrapods after about 370mya
*- by 338mya tetrapods were fully terrestrial
*- Incremental nature of evolutionary process that resulted in the complex of he interrelated
changes set in time, place and environment.
*- Erect back, balancing on two legs, walking and running, though interconnected, are four distinct
entities.
*- Standing was the start of the long series of adaptive changes that was predicated on the
accumulated benefits of the earlier evolutionary phases : primacy of vision, diurnal habits,
taillessness and the spatial mobility of the apes.
*- The piecemeal preconditions for bipedalism were followed by no less piecemeal extraordinary
consequences for our own evolution as humans.
*- An incremental perspective on evolution that culminated in the erectness had no inevitable
connection with adaptations for big brain.- as corroborated by fossil record.
**- Brans enlarged in their own linage.
*- The first bipeds had no need of brains larger than those of apes.
*- The development of cleverness must have been equally subject to incremental change and
equally tied to selection for a particular type of mental versatility.
*- Step by step improvement in cleverness must have had effect on sensory, motor, physiological,
behavioural, mental and neural skills. Each of these modifications must have had its own ecological
and behavioural contexts.
*- Several parallelsmust have existed in the physical and mental development..
*- Staged changes in ecology and behaviour must have corresponded with piecemeal changes in the
way in which evolving humans constructed mental models of the world or the worlds in which they
found themselves.
*- These would have included literal ‘models’ (including the physical constructs we call tools)
whereby they could eke out a living through their own and their social group’s actions.
-------------------------------
Section 3
Page 291 onwards :
**- Homo Sapiens – “wise humans” Darwin broke this mould by anointing us to “lowly origins”
***- With humans sharing erectness (the only measure of separation between hominins and apes),
what other crude measure of our stature remains? 1. The Handy-man made tools more than 2 mya
2. Erect humans – tall and strong – reached islands on watercraft 3. Massive Neanderthals even had
larger brains 4. These hominins could communicate with one another is certain but the degree to
which they could talk and think as we do is still unknown and will remain unknowable. What
distinguish modern humans from premodern ancestors – that are now extinct?
***- Humans physique is more delicate, forehead is higher and my teeth smaller. Compared with
their apishness or their hulking muscularity, we look less like an adult and more like on of their
children – a descendent that has failed to grow up.
**- extended childhood is a trait that runs through almost every stage of our evolution. Of
vertebrates, mammals have the most prolonged immaturity; of mammals, primates; of primate,
apes spend the longest time preparing for adulthood. Hominins continue this trajectory until modern
humans – culd almost be said to be permanently immature. The technology plays a role analogous
to maternal protection in that it detaches is from many of the disciplines of the environment. The
ultimate legacy of bipedalism and emancipation of hands is that we have prolonged childhood and
created an all embracing technological parent.
**- As with other animals, mother’s altruism can be seen as the expression of her drive to protect
the survival of her own genes.
***- in groups or bands that were mostly made up of closely related individuals, altruistic behaviour
could as well be described as “kin selection” as “reciprocal altruism”.
**- We can envisage long lasting, relatively stable social groups in which intragroup behaviour might
have rendered some classes more vulnerable than others but which were mainly threatened from
outsie by predators, enemies, diseases and accidents.
*** - we must seek the secrets of our ecological dominance and the special properties of our mind –
the two are interconnected.
***- All foraging would have occurred in response to a rapidly changing calendar of food availability.
These seasonal changes would have demanded versatility and good judgement as to when to switch
frm one food or one set of skills to another – at the same time trying to continuously expand the
area for food sources.
***- A revolutionary insight into the peculiarities of modern human evolution has emerged from a
study by University of California in SanDiego. They compared the genetic diversity of African apes
and modern humans by selecting a small region of mitochondrial (mt) DNA where mutations are
thought to accumulate at a steady rate. The most significant conclusion to emerge from this
comparison was that there was more mt DNA variation in 55 chimpanzees belonging to a single test
group than in the entire human population. Gorillas show equivalent measures of ancient diversity
to those found in chimps. This evidence proves that our linage has been through a very extreme
form of genetic bottleneck. By comparing the genetic make up of the Neanderthal, scientists have
concluded that at the very start of our emergence as a distincy species – our own bloodline
***- ancestors in Africa were reduced to a mere handful, robbing their descendents f the genetic
diversity.
***- The genetic separation between various species was quantifie by Satoshi Horai and his
collegues. Using mt DNA sequences, scientists found modern humans showed a maximum range of
18 mutations, whereas two chimpanzees species (common and pygmy) were 90 mutations apart,
Chimps and humans were nearly 200 mutations apart, with gorillas chimps were 250 mutations
apart and with orang-utans over 500 mutations apart. The clustering of chimps with humans rather
than with other apes was confirmed while also demonstrating the skimpiness of diversity in humans.
***- The genetic evidence supports the idea of a relatively sudden and surprisingly late emergence
of modern humans from a miinuscle population, popularly represented as a single symbolic “African
Eve” – equivalent to genetic “Big Bang”.
***- The genetic bottleneck in Africa after divergence from Neanderthals raises few questions: How
and when humans spread over the globe? Why did contraction in numbers take place? Where did it
happen? It would have been limited to humans because there is no evidence so far for other
organisms in Africa.
***- The answer to the above questions may lie in the development of exclusive sense of cultural
identity. Such exclusivity may well have been an important factor n preserving the genetic identity of
Moderns whenever they came into contact with other humans. This cultural exclusivity could have
been of particular significance at times when contact with sibling Archaics could have represented a
genetic threat to their fledging identity. They would have defined themselves in terms of their
economies, languages and technologies that served them. These cultural barriers and not genetic
incompatibility would have been the principle obstacle for genetic exchange.
***- The extinction of all other types of humans hints at the endemic intolerance in our species;
there are enough instances of genocide within Homo sapiens to make active hostility toward other
cultures one of our defining characteristics.
**- to offer the explanation for the intolerance of humans – our ancestors might have begun their
existence as the victims of an all out fight, only to become ultimate victors over their unknown
persecutors – hence developing the intolerant exclusive attitude towards others.
*- the paradox of extreme genetic contraction followed by a truly astonishing global expansion.
*- the estimated dates at which Moderns left Africa range from about 100kya to 222kya.
***- The ability to co-operate in larger groups and to diffuse knowledge is generally thought to have
contributed to the long term triumph of Moderns over Neanderthals and Erects. Part of this success
may be attributed to language.
*- Modern human fossils details
***- Walking out of Africa to the ends of the Earth can be seen as the ultimate triumph of homo
sapiens.
Locality and age
*- The contrast between African and non-Africans is highlighted by the fact that modern Africans are
most diverse people on Earth.
**- Two recent estimates agree on primary African- non African split at 190k to 222kya. Other
estimates, 156k,140k,100k,65k may have produced younger dates partly because they ignore
subsequent gene flow back into Africa.
*- In northen winters, people tend to suffer vitamin D deficiency because it is sunshine falling n the
skin that produces the chemical reaction to synthesize this essential vitamin. Among the lethal
consequences of too little vitamin D are rickets and failure in young women to bear healthy children.
Ohysiologists have concluded that paling of the skin favours vitamin metabolism so it must be
significant that the densest distribution of the least pigmented people on Earth coincides closely
with the former boundaries of northen European ice sheet.
***- Our own sweat system is unique in its wholesome switchover from apocrines to eccrines –
which along with speech and bipedalism is described as the truly unique characteristics of humans.
***- Homo sapiens are only one of the 18 species of hominins that survived.
***- Allogorizing the creation story Adam and Eve
***- we have too little respect to the authority of the nature. Science is too often diverted to
increase power over nature rather then understand it on it own terms. We have become too used to
turning to science and technology for new expedients to overcome immediate problems as they
arise.
***- At least 18 species of fossil humans and bipedal hominin have been discovered having their
own separate linage. Oue own line represents an early aberrant offshoot, while most of the others
maintained more of their ape heritage in spite of taking to the bipedal way of life.
*- Uprightness dated to 6 mya
***- Erects having all characteristics of man except big brain –but know use of fire.
***- Humans and near humans are relatively abundant, diverse and regionally localized animals. Our
ancestors were as Africans as the numerous species of antelopes or elephant shrews are today. We
are not just Africans, we are eastern Africans – a single survivors of at least 18 homo species.
**- Humans capacity to talk, think, reflect and draw evolved along the way – which owe their
existence to many staged increments; they are not single mutant genii.
***- Human mental properties followed their own developmental path, one that may not be readily
tied in with the gross anatomical story, except at the very crudest level.
***- It is a general perception that humans have evolved a special niche that is variously
characterised as intelligent, technical, rational and reciprocal.
**- It was the evolution of bipedalism and the emancipation of hands that was followed by ever
enlarging intelligence that led to development of comprehensive set of tools and techniques.
**- The rise of humans led to long term effect of depriving other species of their livelihood by
consuming the same resources and taking up more and more of the living space of other organisms
leading to the eventually elimination of some of them.
**- Humans have had a negative impact on the ecology of environment. : large mammals
extinctions, a dwarfing of the surviving species and a huge increase in the frequency and impact of
fire with corresponding changes in vegetation.
**- The sustained work of digging, weeding, guarding and processing was unlikely to have adopted
by nomadic foragers except under duress.
***- The adoption of agriculture may well have been influenced by declining yields from hunting; but
the main mechanism favouring agriculture would have been the demographic success of it
practitioners. In parallel with herbivores and carnivores, plant consuming, niche-thieves would
always have outnumbered their animals consuming equivalents.
***- We know that the internal “virtual” world that we call imagination is shared and developed
through speech.
***- The beginnings of speech, structured conceptual thought and effective verbal communication
must have developed from faculities that are possessed by many other animals species that still exist
around us.
***- If humans are to survive in the world that gave birth to them, they can ill afford to drift, en
masse, into a series of other virtual worlds. If virtual worlds effectively blind entire peoples to the
ecological realities of their environment, then the need to understand humanities’ perverse
relationship with nature will have to include an effort to understand the perversities of our mental
and conceptual processes.
** - compartmentalization of knowledge and specialized skills – and its effect on humanity
*- The special biological role of humanity is that of a niche thief. Future survival demands much
greater sel-consciousness and more than repentance for our endemic greed for the livelihoods of
others.
***- Our dominance has implicated the disappearance of so many more of our biological cousins.
Our role in their extinction may have been direct or oblique. It is not impossible that the human
induced processes that have served to remove so many of our cousin competitors may eventually
contribute to our own removal. In making life impossible for so many species, we may eventually
make life impossible for ourselves.
***- causes for environmental degradation
***- causes of environmental degradation
***
***
***
END
A natural history of the human mind: tracing
evolutionary changes in brain and cognition
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409100/
The last common ancestor can be reconstructed to have had a brain of approximately 300–400 g that
displayed several unique phylogenetic specializations of development, anatomical organization, and
biochemical function.
With this evolutionary history as precursor, the modern human mind may be conceived as a mosaic of traits
inherited from a common ancestry with our close relatives, along with the addition of evolutionary
specializations within particular domains. These modern human-specific cognitive and linguistic adaptations
appear to be correlated with enlargement of the neocortex and related structures.
Finally, the unique brain growth trajectory of modern humans has made a significant contribution to our
species’ cognitive and linguistic abilities.
‘We’ are Homo sapiens and our species’ intellectual abilities distinguish us from all other animals. Our
technological sophistication, capacity for introspection, and ability to create and manipulate symbols is
unrivalled. We engage in behaviors that are profoundly unique, such as the production of personal
ornamentation, language, art and music, and the performance of religious rituals. This behavioral discontinuity
has prompted many to regard modern humans as standing apart from the rest of nature. Yet, despite our
distinctiveness, ‘we’ are also one among several species of great ape, displaying more than 99%
nonsynonymous DNA sequence similarity with chimpanzees (Wildman et al. 2003), having diverged from each
other approximately 4–8 Ma (Bradley, 2008). Consequently, modern humans share many phenotypic traits
with these close relatives through common descent.
The tension between striking behavioral divergence in the face of phylogenetic continuity presents a puzzle.
Although many authors have discussed the possible selective advantages and evolutionary processes
underlying the emergence of modern human cognition (e.g. Holloway, 1967; Calvin, 1994; Dunbar,
1996; Tomasello, 1999; Tooby & Cosmides, 2005), it still remains a serious challenge to understand how the
unique features of modern human behavior are mapped onto evolutionary changes in neural structure.
Considering the dramatic behavioral differences between modern humans and other animals, it is reasonable
to expect similarly remarkable alterations in brain organization. As Darwin noted in The Descent of Man (1871),
there appears to be a link between our intelligence and our expanded brain, which increased in size by roughly
threefold since the last common ancestor (LCA) shared by hominins (the lineage including modern humans and
our fossil close relatives and ancestors) and panins (the lineage including common chimpanzees, bonobos, and
their fossil close relatives and ancestors). Because a large brain size so clearly distinguishes modern humans,
many theories of human cognitive evolution consider only this single anatomical variable to account for the
myriad specialized behaviors we exhibit (e.g. Jerison, 1973; Dunbar, 1996).
Subtle modifications in neural microstructure and gene expression can have a significant impact on behavior,
even in the absence of large-scale changes in the size of brain parts (e.g. Hammock & Young, 2005).
Evolutionary processes, therefore, can mold behavioral phenotypes using a host of strategies.
In this context, the aim of this article is to examine how changes in brain anatomy and physiology articulate
with unique aspects of modern human cognition. We employ a multidisciplinary approach to trace
evolutionary changes in mind and brain from the LCA to modern Homo sapiens, incorporating evidence from
comparative psychology, neuroscience, genetics, paleoanthropology, and linguistics. By providing a detailed
contrast between the mind of the LCA and Homo sapiens, it is our intent to bring into relief the distinctive
characteristics of modern humans against the background of what is inherited from our most recent ancestry.
Therefore, the paleonotological record for these traits in human evolution is limited to what can be gleaned
from endocranial casts and archaeological evidence
As endocasts preserve only an impression of the external morphology of the brain, critical information
regarding internal neuroanatomical organization cannot be determined. Behavioral abilities, furthermore, can
only be glimpsed opaquely through material remains. However, the paleontological and archaeological records
constitute the only direct evidence of temporal change in morphology and behavior, providing crucial insight
regarding their association. Paleontological evidence, in fact, indicates that major innovations in cultural
behavior were not always linked to upsurges in cranial capacity of fossil hominins. For example, early signs of
animal butchery are found in association with Australopithecus garhi(Asfaw et al. 1999), suggesting that a
small-brained (450 cm3 cranial capacity) East African hominin from 2.5 Ma might have had the capacity to
fashion simple stone tools.
Nevertheless, when a character state is observed only in modern humans and not in any of the other extant
hominids (the clade that includes the living great apes and modern humans), then it is reasonable to conclude
that the modern human condition is derived compared to the symplesiomorphic state seen in the great apes.
The segregation of individuals by sex and age for specific social activities is arguably unique to the great apes –
specifically, chimpanzees – and virtually absent in monkeys, including those with societies that resemble a
fission-fusion social organization, such as the hamadryas baboon.
Whiten and colleagues (1999, 2001) reported 39 different traditions in various African chimpanzee
communities that included tool use, grooming, and mating practices. Some of these traditions were customary
or habitual in some chimpanzee groups but absent in others after controlling for ecological constraints (e.g.
availability of certain raw materials). Using the same systematic approach to the documentation of traditions
in nonhuman primates, van Schaik and colleagues (2003) reported at least 19 clearly defined traditions in
orangutans. This stands in contrast to reports of traditions in monkeys, whales, birds, and fish, where at most a
handful (usually only one or two) have been identified (e.g. song ‘dialect’ in birds and whales). In none of these
cases has the number of behavioral variants reached double digits (Rendell & Whitehead, 2001; Fragaszy &
Perry, 2003).
Although there is always the possibility that such a result is due to over-representation of great apes in the
sample, it is notable that despite many years of research on several monkey species (including macaques,
baboons, and capuchin monkeys), only capuchin monkeys evidence behaviors that potentially meet the criteria
for traditions (Panger et al. 2002; Perry et al. 2003, but see Subiaul, 2007).
Self-awareness
The possibility that different mammalian lineages are ‘self-aware’ presents at least two possibilities: (1) mirror
self-recognition is an emergent property present in species with large brain size and a complex social
organization or (2) there are multiple adaptive functions to the cognitive ability that is measured by mirror-self
recognition and, consequently, this skill emerged independently in numerous mammalian species.
Gaze-following
They conclude that chimpanzees, bonobos, and gorillas are more sensitive to another's line of sight than are
orangutans.
Monkeys generally cannot be trained to use only the human experimenter's gaze cues to retrieve the
concealed reward (Anderson et al. 1995, 1996), whereas great apes can (Itakura & Anderson, 1996). Povinelli
& Eddy (1996a,b) have hypothesized that great apes outperform monkeys on this task because they possess an
automatic response that forms part of a primitive orienting reflex triggered by a reward.
Physical cognition
Some have argued that chimpanzees and other great apes have a more sophisticated understanding of
physical causality than monkeys, as reflected by their tool-use in the wild (Visalberghi, 1990; Limongelli et al.
1995; Visalberghi et al. 1995; Westergaard, 1999). This conclusion is buttressed by the fact that traditions as
they exist in chimpanzees and orangutans are mostly absent in monkeys. And where they exist, as appears to
be the case in capuchin monkeys (Panger et al. 2002; Perry et al. 2003), they comprise only two or three
behaviors, which lack the diversity and complexity that characterize chimpanzee and orangutan behavioral
traditions (Subiaul, 2007; Whiten & van Schaik, 2007).
Such experiments on physical and numerical cognition suggest that there are no significant qualitative
differences between chimpanzees’ and monkeys’ understanding of the non-verbal aspects of number or of
unobservable physical causes. Therefore, the differences between great apes’ and monkeys’ tool-use in the
wild may reflect factors such as greater manual dexterity and fine motor coordination, as well as social-
cognitive variables such as the ability to benefit from social conventions and copy novel motor rules.
Social tolerance
Given the differences between monkeys and great apes discussed above, what may be said about the LCA? We
hypothesize that changes in the paleoenvironment in the late Miocene resulting in a wider distribution of
woodlands produced a trend among the African great apes toward more stable relationships between the
sexes and stronger associations between male kin (Foley & Lee, 1989). The LCA likely lived in an environment
where the patchiness of food led to a wide distribution of females, selecting for male kin to form cooperative
coalitions to defend an expansive home range (Foley & Lee, 1989). Given the evidence reviewed above, we
conclude that the LCA displayed regional variation in certain behavioral traditions, ‘self-awareness’, and an
enhanced ability to follow the gaze of other social agents. We further hypothesize that these behavioral
characteristics are related to increased capacities of executive control to inhibit conventional responses in
favor of social tolerance and seeking novel and flexible solutions to problems. These behavioral abilities would
have been advantageous for a large-bodied, frugivorous, social primate in the late Miocene.
Large brain size
All living hominids have large brain sizes in absolute terms and in some measures of relative size (Passingham,
1975a; Holloway, 1983; Martin, 1983). Similarly, the LCA is expected to have had a brain mass of
approximately 300–400 g. This size is within the range of extant great apes and is close to the cranial capacity of
the earliest hominins (Holloway et al. 2004). Furthermore, the cranial capacities of some late Miocene apes,
such as Dryopithecus, are within the lower end of this range (300–330 cm3) (Begun, 2004). Comparative studies
suggest that positive selection occurred in genes associated with primary microcephaly
(i.e. ASPM and microcephalin) along the phylogenetic lineage leading to the LCA (Kouprina et al. 2004; Wang
& Su, 2004); however, it is less clear whether these genetic variants are related to normal brain size variation
and evolution (Woods et al. 2006).
Taken together, these findings indicate that the neural machinery for processing complex acoustic signals
contained in species-specific communication was present and lateralized in the LCA, providing a scaffold upon
which language functions later evolved.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409100/
