I am never sure why scientists of all disciplines, anthropologists especially, say that the most distinctive thing about humans compared with all other primates is the fact that we walk upright. All right, it frees our hands to do all sorts of useful things such as making tools, carrying things, writing and using computers, but was that an absolutely necessary prerequisite for big clever brains? You can imagine small brained, but erect, ape-like creatures going about their business quite satisfactorily almost as before, eating vegetarian food which their erect posture made it easier to collect, store and eat because their hands are getting better at shaping a few more tools. But nothing world-changing had to happen as a result. That bipedalism seemed so important is only because scientists have been entirely dependent on fossils, and particularly bones, to find out anything about our early ancestors, and why hominids split off from chimpanzees about 6 million years ago. So it seemed obvious that if we found out when primates began to be bipedal that would immediately tell us we were on the right path. Having found Ardipithicus remains that dated between 3 and 4 million years ago, which showed clear evidence of the beginnings of walking on two legs most of the time, the problem seemed to have been solved. But why would this different way of walking on its own inevitably set them on a path to becoming human? It does not even begin to account for the huge explosion of brain size, and its inherent complexity, from 380-610 cc in Australopithecus to 650-900 cc in Homo erectus, about 1.6 million years ago.

I think a lot more than walking on two legs was needed to change the path of evolution. The attribute that really made us human is much more likely to be the use of language. Language fits the bill exactly for the trail of evolution which led to modern humans and their very large complex brains. Language doesn’t fossilize, so you can’t tell from skulls at what point language began. But it did, so it is necessary to look at what else was going on 4 to 5 million years ago. Firstly, it seems that the brain of Ardi was slightly smaller than that of modern chimpanzees, although it might have been larger than the brain of the ape of the time that was destined to become a chimp. Whatever had started it off on a path to big brains may have only just got going then, even though Ardi was well on the way to becoming bipedal. So something else must have been happening at that time, and I think that has to be the acquisition of language.

If you look at how the development of the human brain started, it seems that several things needed to be in place. Firstly, the brain had to get enough of the right sort of food in order to grow so large. Secondly there had to be some sort of selection for bigger brains. Thirdly language structure needed to be hard wired into the brain.

So how did the ancestor of homo, if it were Ardi, get so much food? Vegetarianism is not the most calorific of diets and so their diet needed to change, to use either meat or seafood.   Was Ardi a good enough hunter to be able to kill large animals? He still wasn’t that good at running, certainly not to out-run large animals and then kill them. What about seafood? That is well known to be nutritious, calorific and contain exactly the right fats to nourish the brain- an equal ratio of omega 3 and omega 6 fats. Many skeletons of ancient hominids have been found on the coasts, and middens of seashells and other evidence of seafood have been found round them. They would certainly need a lot of such food, and females could collect them as well as any male, so there would have been no need for complex hunting patterns.

It is a fact that the brains of hominids doubled in size over those 3 million years, so their babies’ skulls needed to grow too. But there was a problem. The demands of bipedalism resulted in the female pelvis outlet being smaller, not larger – so walking on two legs was never the most important development for humanity; if anything it was a disadvantage.

If the skull grew too large this would result in obstructed labour with the deaths of baby and mother – hardly a recipe for success of the species. So something had to happen; there was selection for those babies that got delivered earlier, and so babies were born more premature. Not so premature that their other systems such as breathing in air were compromised, but earlier so that they could easily pass through the birth canal. Note that this is never a problem in modern day chimps or any other ape – there is no tight fit and birth is very easy for them. But obstructed labour can happen in humans even nowadays with disastrous consequences if modern obstetrics isn’t there to redeem the situation.

But why was there selection for big brains anyway? Brains are expensive to maintain, and no species would invest so much in them if there weren’t a reason. Genetics tells us that there may have been sexual selection to do with Y-chromosomes and X chromosomes each trying to outdo the other. It is very complicated; I won’t go into it now, though it did appear to me that something of this sort might explain the tremendous antagonism between the sexes that permeates some cultures even today.   But while the theory may explain the genetic mechanism, I am not sure this really explains why brains grew so big.

What were babies doing with these larger brains in those first years that was so essential? They certainly weren’t doing much with their bodies – all right, they were learning to sit up, control their arms and legs and hands, and walk, but other primates do all that in a much shorter time. The thing that would enable the species to be more successful was much more interesting than that –they were learning to speak. Now, by the time children are two they have now laid the foundation for a complete language with grammar, syntax vocabulary and all the speech sounds that go with it. But it can’t have happened all at once. It must have taken a considerable time to do.

Many scientists think that proper grammatical language started much later. Some even think that Neanderthals had only very rudimentary speech. But from a linguistic point of view this seems very unlikely. Stephen Pinker argues for a language instinct starting quite early in prehistory, and certainly more than 2 million years ago. His point is that language isn’t taught in the same way as, say, reading is. It seems to be absolutely instinctive, that babies pick language up extraordinarily easily and rapidly. It predates almost all other skills other than gross motor ones like walking and running, and continues at an exponential pace throughout our childhood. So how did it come about?

Consider the well-known fact that adults are not able to learn new languages anything like as easily as children. If you put a group of people permanently in an environment where there is no common language, these people will eventually learn to communicate; but this will be in a very simple way with very little grammar. Such languages are called pidgins and are used all over the world when they are needed. If these people then have children and they talk to them in pidgin, or they learn pidgin from other children, then these children will superimpose grammar on to the pidgin, making it much more versatile and able to express things much more clearly. The next generation of pidgin speakers then speaks a creole, a proper language, on a par with any other language on earth. This is one of the reasons that Stephen Pinker thinks that language is an instinct, not a learned behavior. All children will learn to speak properly and grammatically unless particular areas of their brain are damaged in some way – even children who are way behind their peers developmentally. For those interested in grammar, the basic bit that seems to be hard wired is the ability to hold in the mind a dependent or “relative” clause and to be able to incorporate it into a sentence which conveys the meaning. Just think of a child discovering a way to say, “I don’t want the food that we had in the cave yesterday, I want the food from this tree today!” Then adults could also say “The herd of animals we saw by the river a week ago is now near by”. Such a group with this ability would immediately have an advantage over other groups who could only say that the herd week ago is now nearby. This basic bit of grammar goes far beyond just naming things or actions, and would be the forerunner of language as we know it. Now once this bit of crucial brain organisation was achieved, real communication could develop. As the children of the hominids developed this ability (and the adults certainly couldn’t do it) then that gave the now grown adults the ability to cooperate in many, many ways and be more successful in feeding themselves and reproducing. This would then give a huge impetus for the continued growth of the brain.

Between conception and age three, a child’s brain undergoes an impressive amount of change. At birth, it already has about all of the neurons it will ever have. It doubles in size in the first year, and by age three it has reached 80 percent of its adult volume.

Even more importantly, synapses are formed at a faster rate during these years than at any other time. In fact, the brain creates many more of them than it needs: at age two or three, the brain has up to twice as many synapses as it will have in adulthood. Once language has been wired in, the more connections that can be made within the brain, the more opportunity for complex group activities would result. This process would have developed gradually generation by generation, and this would really be the driving force behind the increased size of the brain, regardless of what the X and Y-chromosomes were fighting about.

But we are still missing a bit of the story. It is well known that it is impossible to teach chimpanzees to speak. Years of work have all proved negative. It isn’t that chimps don’t understand how to communicate – they have rich signing gestures and behaviours that make it completely clear to others what they are getting at. They can also make many of the sounds essential to speech – most consonants and a few vowels, certainly enough to make understandable words. But what they can’t do is control their breathing in order to make sounds voluntarily. This may be anatomical, and associated with the descent of the larynx so that air can go through the larynx under the brains control to start the production of sounds. It certainly isn’t an instinct that chimps have, or any idea how to do it. The only explanation of this that makes sense to me is that which Elaine Morgan explains in her book “The scars of evolution”. While the ancestors of Ardi or similar small hominids were spending a lot of time at the seashore, getting all those wonderful fats in the right proportion for the brain, they learned to dive. Diving means getting the ability to hold your breath voluntarily while you are under water and let it out when you surface. Again, that is something with immediate benefits for the individual and group – more fish, more food. This was the fundamental difference that made it possible for the species to start on a path that developed a spoken language gradually as hominids spread into different habitats.

So it was the children who invented the language, little by little, noun by noun, sentence by sentence. And when they became adults the group benefitted from this and survived and prospered. But most likely they continued to prosper near the sea which provided their ideal diets, Only when a species developed which could not only speak but also run, could Man the Hunter finally put in an appearance. To hunt on the savannah he would certainly need to cooperate with his group in order to develop a strategy that could bring sufficient good protein to the whole group to ensure the expensive brains got enough nurture.

We shouldn’t think of everything human being the result of what adults do; the foetus, new-born and infant have their own natural selection going on, which chooses the bits of evolution that improve their chances of their survival even at the expense of the adult. And it is in those early years, by those babies, not their parents, that grammar and full language was developed for the human race.

So linguists believe there is a language instinct operating in small children, which underpins the structures of all languages in the world. There are enough similarities in basic grammar in all languages to be sure of this. We don’t know whether this happened just once or several times, with newer and better structures being selected for. And we know that, sadly, this hard wired ability to learn languages disappears in childhood. Up to the age of seven children will learn languages very easily, but it becomes progressively more difficult to learn a new language until after about 13 or 14 years it becomes impossible to learn new sounds and accents, and grammar becomes a chore to be learnt, not an instinct at all.

I am intrigued as to what will happen to the mental processes of the next generations. Children in developed countries now use I-pads at 2, and learn pattern recognition and reasoning well before they used to. The adults they become will have a head start over adults now in many areas of brain function. In the developing world children’s IQ results are showing an increase too, as more get an education, so that they may well start catch up with their peers in developed countries, whose IQ rise is beginning to plateau or even fall. Early years of childhood have always been even more important than we realize, and investment here is paid off many times in the future.

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Apes and Women

References

Elaine Morgan: The Descent of the Child
Genome: Matt Ridley
Rice WR Holland B: The enemies within, ICE and the intraspecific Red Queen Behav Ecol Sociobiol 41 1-10 https://www.researchgate.net/publication/227329481_
The Language Instinct: Stephen Pinker
Elaine Morgan: Scars of evolution
Richard Lynn, John Harvey: The decline of the world’s IQ http://www.iapsych.com/iqmr/fe/LinkedDocuments/lynn2008.pdf