The Puzzle of Hyper-Intelligence

Maybe big, efficient brains were just an evolutionary fluke.

I suppose that I’m not living up to the Bloggers’ Code by passing up the opportunity to pour forth my immediate thoughts on the current Big Internet Topic. My excuses are (i) assassinations, completed or attempted, are depressing and (ii) we know almost nothing at this point about the would-be assassin’s motives or plans. It certainly looks like one of the strangest murder plots ever. What, for instance, did the murderer hope to gain by carrying no identification and booby trapping his car with explosives? There was no rational prospect of his surviving the deed, and if there had been, the time needed to remove the bombs from the getaway vehicle would have thwarted escape.

Oh, I’ll say one more thing before getting to my real topic. Winston Churchill’s quip “There is nothing more exhilarating than to be shot at with no result” is being widely quoted. No doubt that was true for Sir Winston. For ordinary mortals, exhilaration is probably the last emotion triggered by having a bullet take off half of one’s ear. Regardless of his faults, Donald Trump scores high in Coolness Under Fire.

So much for current events. Let’s now turn to an event more momentous than a failed assassination, albeit it happened over a long time span hundreds of millennia ago, viz., the evolution of creatures with a level of intelligence vastly superior to any that of any previously existing species.

The possessors of that “hyper-intelligence” are, of course, ourselves, members of the species Homo sapiens. We (or at least I, and probably you) have taken it for granted that “survival of the fittest” spurred the dramatic increase in human intelligence. An article in New Scientist (a very woke publication but not lacking in interesting information) disputes that assumption:

Nobody doubts that Albert Einstein had a brilliant mind. But the Nobel prizewinner, famous for his theories of special and general relativity, wasn’t blessed with a big brain. “It was smaller than average,” says Jeremy DeSilva at Dartmouth College in New Hampshire.

This seems surprising. Big brains are a defining feature of human anatomy, and one we are proud of. Other species might be speedy or powerful, but we thrive using the ingenuity that comes with a large brain. Or so we tell ourselves. Einstein’s brain hints that the story isn’t so simple – and recent fossil discoveries confirm this. Over the past two decades, we have learned that small-brained hominin species survived on Earth long after big-brained ones appeared. Moreover, evidence is growing that they were behaviourally sophisticated. Some, for instance, made complex stone tools that could probably only have been fashioned by individuals with language.

These discoveries turn the question of human brain evolution on its head. “Why would selection favour big brains when small-brained humans can survive on the landscape?” says DeSilva. Neural tissue consumes lots of energy, so big brains must surely have brought benefits to the few species that evolved them. But what?

The implication is that the intellect that could compose symphonies, solve equations, understand subatomic particles and write speculative articles about human evolution arose at a time when it was of no immediate use, then remained dormant until minutes before yesterday.

Our distant ancestors, inhabiting African savannahs, had no need for the accouterments of modern civilization. The skills that their survival did require were communication, an aptitude for planning and the ability to fashion elementary tools. All of those were within the intellectual capacity of now-vanished species related to ours but with much smaller, less developed brains.

Until a few decades ago, the explanation seemed obvious. Many researchers assumed that the hominin evolutionary tree looked fairly simple, particularly following the evolution around 2 to 3 million years ago of the first species belonging to the genus Homo from the more ape-like hominins. The idea was that only one species could occupy the environment at any one time, says Philipp Gunz at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. So, Homo habilis appeared to thrive until it was replaced by Homo erectus, which was superseded by Homo heidelbergensis, which itself was supplanted by our species, Homo sapiens, in Africa and by the Neanderthals in Eurasia. In each case, the successor species had a larger brain than its predecessor. Researchers rarely questioned the idea that big-brained humans were smarter and evolutionarily superior to their small-brained ancestors.

But we now know that small-brained hominins lasted a long, long time, overlapping Homo sapiens by tens of thousands of years. The oldest Homo erectus fossils date back nearly two million years, the latest from 110,000 years ago, 100,000 years or so after the first Homo sapiens. Earlier, Homo habilis survived for a million years, coexisting with Homo erectus for about half of that period.

It isn’t obvious that bigger brains conferred a decisive evolutionary advantage. Moreover, they came with drawbacks.

Adding to the puzzle is the fact that big brains carry some clear disadvantages. They are demanding to run: ours consume around 20 per cent of our daily energy intake despite accounting for just 2 per cent of our body mass. Moreover, a baby with a large brain is tricky to deliver and to raise. “Childbirth is difficult,” says DeSilva. “And when you’re trying to feed this infant with its growing brain, it’s an energetically exhausting endeavour.”

There is a further indication, not discussed by New Scientist, that tells against the idea that hyper-intelligence is a superpower adaptation. Almost every valuable biological trait has evolved more than once. Insects, reptiles, dinosaurs and mammals each learned independently how to fly. Endothermy (internal temperature regulation) arose in mammals and in birds (and even in some fish). The same is true for diet, tooth types, forms of locomotion and much else. The DNA revolution revealed that numerous classifications based on anatomical features were wrong; the resemblances were due to parallel evolution.

Intelligence is different. At a simple problem-solving, intra-species cooperative level, it is found quite widely. Beyond that – the intelligence of dolphins, chimps, elephants, dogs, et al. – lies what we might term “higher intelligence”, distinguished by the ability to fashion tools for future use (as opposed to opportunistically utilizing sticks and rocks to deal with an immediate need). The next step is hyper-intelligence, the mental agility found in Homo sapiens, (very likely) in the Neanderthals and (perhaps) in the all-but-phantom Denisovans, without which civilization is impossible.

Natural selection does not, however, have civilization as its goal. Its only “purpose” is passing an organism’s genes on to the next generation. Higher intelligence and hyper-intelligence had a poor record on that score until after civilization came to be.

Outside of a limited group of species descended from great apes, there is no spoor of higher or hyper-intelligence anywhere on this planet. What is more, except for Homo sapiens, every known species with those capabilities has died out within a relatively brief period on an evolutionary time scale, and, of the twenty or so such species that have existed, only our direct pre-human ancestors have left descendants. That is a remarkable record of evolutionary failure.

The most conspicuous mark of that failure has been discovered in the human genome. Modern humans are remarkably alike genetically. As one study of chimpanzees, our closest surviving relatives, put it –

Surprisingly, even though all the chimpanzees live in relatively close proximity, chimpanzees from different populations were substantially more different genetically than humans living on different continents. That is despite the fact that the habitats of two of the groups are separated only by a river.

Lack of diversity is evidence that ancestral populations were consistently small or collapsed dramatically at some point. Chimpanzees evidently never suffered either fate (until, alas, the present day). Recent research suggests, by contrast, that humanity’s ancestors suffered a 99 percent population reduction about 900,000 years ago and that their numbers didn’t recover for over a hundred thousand years. That was in the era of mere “higher intelligence”. Hyper-intelligence fared no better.

Geneticists studying many different parts of the human genome have concluded that the past effective population size (that is, the number of reproducing females) averaged only 10,000 individuals over the last one million years, and was as low as 5,000 around 70,000 years ago.

It appears, then, that higher and hyper-intelligence were barely sufficient to cope with the challenges of unmodified nature, challenges that many less sapient species survived with ease. Yet behind-the-scenes genetic variations, without contributing to immediate survival, led to Plato, Aristotle, Newton and Einstein. That was an incredibly lucky draw in the biological lottery. One can’t help but suspect that we misunderstand either the data or the workings of evolution or both.