What does it mean to be human?
In the 17th Century, René Descartes' statement "Cogito, ergo sum (or "I think, therefore I am")"[i] implied that thinking confirms human existence. In our own time, Neil MacGregor presented another view of human existence when he suggested that our increasing dependency on the things we create differentiates us from all other animals; we are characterised by what we make.[ii]
What humans can do ... and other species can do also
Human beings think, solve problems and use tools. Early human beings could pick up and use objects lying around them to secure and prepare food. Humans could also reshape objects, remember the past and imagine future possibilities. Human beings could co-operate with other human beings.
But so could other animals. Observations indicate that many non-human animals are much smarter and more adaptable in their behaviour than was once supposed.
Some birds can solve problems. A New Caledonian crow can obtain food by forming probes from leaf stems to turn over parts of trees where fat grubs hide.[iii] Hawaiian crows seem to be able to perform similar tasks.[iv] Pacific octopus can build up rocks to block their underwater dens (and they can, it seems, amuse themselves by playing games). The famous bonobo ape Kanzi demonstrated some understanding of spoken words and a capacity to follow new instructions. He could break a piece of 'flakey' stone to produce a sharper edge which he then used to cut cord.[v]
Carel van Schaik described an orang utan who was determined to gain entry to a shed containing bananas. She tried various objects which were lying around and which could be inserted between planks of the shed in order to try to pull them apart.[vi]
Many animals live within and depend on complex social networks.[vii] They can co-operate even between species. Fish have been observed signalling to each other and co-operating across (fish species).[viii]
The power of recall of elephants and dolphins has been noted. Studies have shown that sheep can remember faces and recognise a particular face more than three years after the encounter.[ix]
The differences between humans and other species are ...
Yes, animals can solve problems, can pick up objects to use as tools, can co-operate with others and can remember. But from early days humans went further. Eventually humans not only picked up objects which they found lying around in order to use them; they modified the objects. About 2.6 million years ago someone used one stone to chip the end of another stone and then used the sharper edge that resulted as a cutting tool to strip the flesh of dead animals from their bones; to butcher meat.[x]
Another vital aspect of the difference is the way early humans used their two hands in different but complementary ways, e.g. in making axes: one hand to grip the stone to be reshaped, the other hand to hold the stone being used to chip at it. This different but complementary use of the two hands is particular to humans. Chimpanzees appear to be unable to master this skill.[xi]
Eventually - not immediately - humans improved on these chipping
tools. About one million years later,
some one produced a finer stone axe - thinner, more symmetrical, more
effective, more thought out
Humans learnt (gradually) to control fire; first for security, to scare off wild animals; then to cook raw meat; then to help shape tools.
Humans used and manipulated materials in other ways, changing
them to what they had not been before.
In 2012 Erin Wayman reported that a skull containing an unusual
substance had been found on the coast of
Why did other species, or at least our nearest relatives, the chimpanzees, not make similar progress?
● One explanation is that human beings lived in larger groups in which there were more opportunities to learn from each other; to demonstrate new possibilities to each other: to co-operate.
But our early ancestors lived in small, isolated populations.[xiii]
Although that may have slowed human progress, it did not prevent it. And
● Another explanation of the differences is that childhood is much more extended among human young than among other species, allowing more opportunities for play with others, and for learning from play. Carel van Schaik (2004) argued that a slow life history was a pre-condition for cognitive evolution.
But chimpanzees also have long childhoods, and orang utans even more so. Orangutan infants are not weaned until they are some seven years of age. Carel van Schaik (2004) judged that orangutans live their lives more slowly than any other mammals.[xv]
● Was bipedality (walking on two legs) the starting point for the transformation of the human species? It leaves forelimbs (hands) free to grip and, in time, to manipulate.[xvi] Steve Olsen (2002) speculated that bipedality may have been a key factor in the evolution of dramatically larger human brains.[xvii]
But bipedality was not unknown among animals before the emergence of human beings. Simon Conway Morris pointed out that large brains, the use of tools and bipedality are not specific to human beings; and that the ability to use the forelimbs for skilled manipulation is not restricted to the 'higher' primates.[xviii]
● What effect may monogamy have had on human development? Robin Dunbar believed that monogamy helped humans to evolve into larger brained creatures. He noted a relationship between brain size and mating systems across various species, with monogamous species having significantly larger brains than species that were promiscuous / polygamous. He suggested that monogamous relationships demanded more understanding of partners and therefore a more active brain.[xix]
Of course most animals species are not monogamous but some are, and they are varied: the Azara's owl monkeys of South America (among whom fathers assume much of the child care responsibilities);[xx] Lar gibbons; mute swans; the giant Malagasy rats of Madagascar; albatrosses; the California mouse; black vultures; shingleback skinks; Sandhill cranes; prairie owls; several cichlids, including Convict cichlids (fish!); Kirk's dik-dik (an African antelope).[xxi] The brain capacities of these species have not developed as has human brain capacity, so monogamy is unlikely to have been a primary cause of human brain development even if it may have facilitated it (and can we be sure that monogamy is a cause rather than simply an effect?).
● Body hair / nakedness and brain development: Nina Jablonski suggested that shedding body hair - nakedness - was a critical step in humans "becoming brainy. [xxii]
Keeping cool is a big problem for many mammals. In particular brains - "our most temperature sensitive organ" - can be damaged by overheating. Nina Jablonski suggested that loss of hair was an adaptation to a changing environment and the development of savannah. They had to travel longer distances in search of food and water; and the adaptation to this experience helped to make possible the enlargement of the human brain.
However, Professor Jablonski acknowledged that various species had evolved to shed fur in response to their environments without a development of brain capacity to match that of humans. They included subterranean mammals such as naked mole rats; marine mammals which swim long distances such as whales and dolphins; large land mammals such as elephants and hippopotamuses. So, for humans, shedding body hair may have facilitated brain development but is unlikely to have been a primary cause.
Was meat eating a starting point for the transformation of the human species?
Briana Pobiner (2016)[xxiii] asserted that meat eating (or more importantly regular meat eating) was one of the pivotal changes in our ancestors' diets: it led to many of the changes that make us human. Chimpanzees also were meat eaters, but occasional meat eaters; and without the human focus on developing the means of procuring meat. There was a progression in the early use of tools for scavenging meat from animal carcasses; and later in the use of tools to facilitate the cooking of meat.
Meat eating may have been especially important in the development of human brain capacity. Over six million years of human evolution, human brain size increased by 300% - although not relative to body size. The shift to eating cooked meat was "unquestionably" responsible for a revolution: the biggest increase in human brain size in our evolutionary history appears to have come after the earliest evidence of the use of cooked meat. The cooking of meat released more of some nutrients and reduced the amount of time needed to produce the same number of calories.
Conclusion: what separates humans from other species? I
It has been said that what separates humans most distinctly from other species is social behaviour; and in particular the use of symbols for expression of self and communication with other humans.[xxiv]
There is a recurrent theme of progress, of moving to another stage, in human capacities. But the more that humans' understanding of the world progresses; the more that humans' manipulation of things and materials around them progresses; the more that humans interact with and exchange with other humans; then the more that humans will need to develop tools of expression and communication with other humans. Increasingly they will need to use symbols.
Perhaps humans' capacity for symbolic and co-operative behaviour promoted the emergence of language. Mark Paget in New Scientist argued that language is symbolic: "... sounds stand for words that stand for real objects and actions."[xxv]
Conclusion: what separates humans from other species? II
It could be said also that what separates humans most distinctly from other species is how they use natural objects / objects occurring in nature: stones, branches, twigs etc. Not only did humans pick up natural objects to use as tools (as did various other species) but they also reshaped them: they used one object to help reshape another object. They combined objects and materials to create new materials.
Again that recurrent theme of progress, of moving on to another stage in human capacities. David Robson[xxvi] illustrated the steps by which humans thought about and developed the use of tools by describing hand axes from different periods of human history: how their manufacture progressed over time from a piece of jagged rock reshaped by chipping with another rock to achieve a jagged edge for cutting: to axes which half a million years ago began to embody a more systematic way of working, carefully calculated and varied: one action to make way for another action, and choosing a goal, an idea of what you want to produce, and the series of linked smaller actions and the planning to get there.
Bruce Bradley of
Conclusion: the capacity to imagine
What began the process? Were humans the species who happened to chance upon / grow into meat eating, tool making, language, memory; or the species who were pre-disposed to look, to consider the opportunities?
Humans used two hands for making stone axes: one hand to grip the stone to be flaked, the other hand to grip the cutting stone. Bruce Bradley considered that the dexterity and motor control needed to use two hands in these different but complementary ways were not seen in other apes. Chimpanzees struggled to master this 'complementarity' even after training.[xxix]
Colin Ledsome (2016) gave another example of human dexterity and complemtarity in using two hands: in making string and in making knots by twisting plant fibres together.[xxx] This process illustrates again the human capacity for imagining future possibilities and then developing plans and choosing actions to make those possibilities happen, such as in knitting and hand weaving.
What makes humans think of using two hands differently when other species don't? Is it because humans had an inherent ability to use two hands differently when other species could not or would struggle to do so? As far as chimpanzees are concerned, is it because one chimpanzee hand, or the other hand, or both are incapable of one of the complementary movements required? Or is it because chimpanzees cannot see the point and ask, "Why - where is this leading?'
Humans could think of the possibility of something being brought into existence which had not existed before them; or of an object being made to exist in a state that was different from the state in which it existed before.
Not only could humans exercise powers of memory and recall: humans could imagine future possibilities. It has been argued that human memory has evolved to imagine what might be and that only humans have the capacity and flexibility to imagine all kinds of futures.[xxxi]
Humans, or an individual human being, could do something that had a future possible outcome rather than an immediate or present outcome only because they saw future possibilities. Humans developed technology far beyond what other species did, and developed dexterity and motor control to match (or the other way around); but the process began with a "What if ... ?".
January 2017, revised May 2017
(See also 'Postscript: the power of imagination and atoms')
© Co-operation & Community 2017
[i] Discourse on method. 1637
[ii] A History of the World in 100
[iii] Virginia Morell. 'Minds of their own'. National Geographic Magazine, March 2008. p. 52
[iv] New Scientist, 24th August 2016. p. 16
[v] National Geographic Magazine, March 2008. p.55-57
[vi] Carel van Schaik. Among
[vii] Lee Alan Dugatkin and Matthew Hasenjager. 'The Networking Animal'. Scientific American. June 2015. p. 40
[viii] Alison Abbott. 'Clever Fish'. Nature, 28th May 2015. p. 413
[ix] National Geographic Magazine, March 2008. p. 47
[x] David Robson. 'The Story in the Stones'. New Scientist, 1st March 2014. pp. 34-36
[xi] ibid, p. 36
[xiii] 'Inbreeding shaped human
evolution'. New Scientist, 30 November 2013.
p. 8; 'People few and far between
[xiv] From Journal of Human Evolution, 2013: reported in Nature, No. 508, 17 April 2014
[xv] Carel van Schaik. Among
[xvi] Tim Radford. 'Book review'. Nature, 7th November 2013. p. 33
[xvii] Steve Olson. Mapping
[xviii] Simon Conway Morris. Life's Solutions: inevitable humans in a
[xix] Robin Dunbar. Human
[xxii] Nina Jablonski. 'The naked truth''. Scientific American, Autumn 2016. pp. 52-59
[xxiii] Briana Pobiner. 'Meat eating among the earliest humans'. American Scientist, Vol. 104, Mar - Apr.2016. pp. 110-117
[xxiv] Mark Paget. 'The eloquent ape'. New Scientist, 6th February 2016. p. 28
[xxv] ibid. p. 26
[xxvi] David Robson. 'The story in the stones'. New Scientist, 1st March 2014. pp. 34-39
[xxviii] Dietrich Stout. 'Tales of a stone age neuroscientist.. Scientific American, April 2016. pp. 24-25
[xxix] David Robson. 'The story in the stones'. New Scientist, 1st March 2014. p. 36
[xxx] Colin Ledsome. Letters. Scientific American, August 2016
[xxxi] 'Memory'. New Scientist, 6th October 2012. p. 35