Human Evolution
TAKE UP AGAIN our trichotomy—Plato, Aristotle, Kant. In respects, since these are such long-standing traditions, one expects to find merits in all three. Why else would they have persisted? In respects, since the science has moved on so dramatically—I refer now to Darwinian evolution through selection—and since the traditions were established before this great move, one expects to find none taken alone entirely adequate. This is true on both counts. Start with Plato. I myself have trouble with the Christian God and indeed with all and any gods. But this is by the by. The point here is that the Platonic tradition certainly captures important aspects of the forward-looking nature of the world. The catch is that in today’s science—in today’s Darwinian science—any kind of nonmechanical understanding is ruled out. You might think that God stands behind things, but that has to remain your opinion. So long as your deity does not flagrantly conflict with science, or so long as you think you can reconcile your deity with science—I for one am with that former professor at Calvin College in simply not seeing how you can simultaneously believe in an original Adam and Eve, crucial for the Augustinian position on original sin, with the history to be presented in this chapter—you are entitled to that opinion. Unfortunately, it isn’t science, and you need to fill the gap now that God is no longer part of that picture.
Carry on with Aristotle. I have much sympathy for this position. If one means simply principles of ordering, then I am inclined to think that these properly supplement a Kantian position, explaining why it is that we can profitably think heuristically about ends and purposes. If it means anything more—as it clearly does to most of the people discussed in chapter 8, and as I am sure it does for Aristotle—then worries arise. If one makes Aristotle entirely secular—which he himself was not—then one runs afoul of this organic nature of reality. You have still got the job of explaining the principles. Is order for free really that plausible? Doesn’t all experience point to the truth of Murphy’s Law? If it can go wrong, it will go wrong. Without design or something equivalent, then nothing functions properly, and blind law without direction cannot do the job. Candidly, anyone who believes in ZFEL is probably ripe for Father Christmas. They think that lowering the taxes of the rich helps the poor. The world doesn’t work this way, folks—it really doesn’t. As Henry King discovered to his chagrin, string ties itself in knots. On its own, it doesn’t coil up nicely.
Which brings us to the third option, the Kantian approach. This fits with a mechanistic view of reality, while at the same time taking purpose, teleology, as fundamental and irreducible. You are not going to get rid of it, nor should you. The problem is, why does this work? We know the answer. Natural selection! This produces design-like effects and yet is entirely mechanistic. It shows why Murphy’s Law is not all-conquering. There is order in the world, produced by natural selection, and we react to it. Whether or not this means that there is or was progress up to human beings is at least debatable. Obviously, natural selection could produce humans because it has produced humans. The question is whether there is any necessity to this process or whether it was just accidental, be it one-off or repeated many times in this or other universes. Stress again, though, that there is nothing in our science or our philosophy that gives Meaning to the world. You might bring Meaning to the world, but that is another matter.
I come therefore to the rest of this book. Moving on now beyond the history of why we have arrived at this point, I want to explore what the Kantian/Darwinian perspective implies for, makes clear about, us humans. What does it mean for us as thinking beings? What does it mean for us as religious beings? What does it mean for us as philosophical beings, interested in knowledge (epistemology) and morality (ethics)? What does it mean for us as human beings, cast naked into the Darwinian world? It is to these questions that I turn, as background starting with what we know of our own history.1
Human Evolution
Mentioned already was that Charles Darwin was absolutely convinced of the fact of human evolution and as soon as he had discovered natural selection was applying it to our species, to our minds and powers of thought no less. However, in the Origin he was cautious, wanting first to get the main details of his theory laid out for all to see and only at the end pointing to the implications for humankind. This did not stop others from getting on the bandwagon, and although in the Descent Darwin had much to say that was both new and interesting—notably about sexual selection—by then he was entering an already well-plowed field. Naturally, the early parts of the book were concerned with making the straightforward case for human evolution, showing how it is reasonable to think—especially on the evidence of homologies—that we and the higher apes are close relatives and that we came jointly from organisms more primitive. “It is notorious that man is constructed on the same general type or model with other mammals. All the bones in his skeleton can be compared with corresponding bones in a monkey, bat, or seal. So it is with his muscles, nerves, blood-vessels and internal viscera. The brain, the most important of all the organs, follows the same law, as shewn by Huxley and other anatomists.”2 No one, then or now, thought that our ancestors are alive still. The point is that we did come from monkeys, which in turn came from other mammals.
The two most distinctive things about humans are our large brains and our bipedalism. There are other distinctive features, for instance, being continually sexually receptive, but other than for teenagers, these don’t count quite as high as being able to think and to walk upright. Darwin seized on them and suggested (what we shall see we now believe on good evidence) that bipedalism came before the explosion of brain size. He also believed (what we shall see we now believe on good evidence) that human origins lay in Africa. This was a lot more controversial. Many people would have much preferred Asia. The Chinese may not be Europeans, but they are certainly a step up on Africans. What Darwin did not have was any good fossil evidence of human evolution. When people referred to the “missing link,” it was always that empty gap people had in mind—a gap perhaps made even more obvious and pressing by the discovery in the early 1860s of what was to become to this day one of the most famous of all linking fossils, Archaeopteryx, the reptile with feathers. From discoveries made in Europe in the years before Darwin, people knew about Neanderthals, but although they fit nicely into conceptions—from their fossils they do seem rather brute-like—no one was really convinced that they were an entirely different species from Homo sapiens. Indeed, some were inclined to think that if you went to the west coast of Ireland, you might well find representatives.
It was not until the end of the century that Eugene Dubois, a Dutch doctor and paleoanthropologist—as students of human evolution are known—digging in the Far East, found an indubitable specimen of a protohuman.3 Pithecampothrus erectus or “Java Man” really was more primitive, although today we show that it was not that different from us by including it in the same genus as ourselves, Homo erectus. One thing that did convince was its place of discovery. In South Africa in the 1920s, when Raymond Dart, another doctor, started pushing the claims of a fossil found down at the bottom of the continent, Taung Baby, he had considerable difficulty in persuading people that he had something significant.4 His task was not made easier by the biggest fraud in the history of science, Piltdown Man, a supposed ape-human found in England in the second decade of the century, and only unmasked in the 1950s. Eventually Dart’s discovery was appreciated for what it was—a protohuman (these are known as “hominins”) sufficiently aged that it was given a new genus, Australopithecus.
Then in the 1950s and beyond, thanks particularly to the labors of the indefatigable Leakey family, the fossils started to pour forth from central Africa, establishing beyond a doubt the place of our origin. American researcher Donald Johanson was at the heart of what is probably the most exciting discovery of them all—he certainly thinks it was the most exciting discovery of them all—the little biped nicknamed “Lucy.”5 She lived in Ethiopia just over three million years ago and had a brain about the size of a chimpanzee’s. Be careful to understand what this means. Her brain was about 450cc as opposed to ours, about 1200cc. (Neanderthals’ are slightly larger!) It does not mean she had a chimpanzee brain. By the indentations on the insides of skulls, you can tell quite a lot about the brains themselves, and it seems clear she had a brain on the way to being human. She really was the paradigmatic missing link, especially when researchers discovered that although she walked upright, she was better adapted at climbing trees than we. Although Lucy—now classified as Australopithecus afarensis—is very important, it is improbable that she is literally our ancestor. We now know that evolution is much more given to divergence—producing bush-like phylogenies (histories)—than simple unilineal change from one form to another. So Lucy would have been one of a number of species or subspecies, very closely related, one of which led to us.
Although still somewhat controversial—causing at least as much public interest as Lucy—was the discovery in the East, on one of the islands of Indonesia, of Homo floresiensis, a small humanlike being that stood about three feet six, with a small brain but with relatively large teeth and feet, that was, naturally, at once christened the “hobbit.”6 What makes this little being so interesting is that apparently it was thriving in the last hundred thousand years, and, although current opinion is inclined to set the date back a bit, may well have gone extinct less than twenty thousand years ago. This means that it would have coexisted with modern Homo sapiens, although there is no reason to think that there was actual physical overlap.
Starting about fifty years ago the study of the past was transformed by the coming of molecular biology. Already people were using physicochemical techniques to provide absolute dates of events in the past—rates of radioactive decay could yield much that is simply not there in the fossil record. Then it was realized that rates of genetic change at the molecular level could reveal much about relationships that could not be discovered from the fossil record alone. This was due primarily to the neutral theory of evolution, the brainchild of the Japanese evolutionist Moto Kimura, who reasoned that whether or not genetic drift occurs at the physical (phenotypic) level, at the molecular level a great deal of change would be, as it were, beneath the radar of natural selection, and so this essentially random change could be used as a calendar to record times of divergence and so forth.7 Combining the information from radioactive studies with the information from neutral molecular studies, one had a very powerful tool to study the past and to come up with new findings.
None more than in the study of human evolution. Virtually overnight it was seen that the human line broke off from the great apes a lot more recently than anyone had hitherto dreamed, only about five or six million years ago. Moreover, we humans are more closely related to chimpanzees than chimpanzees are to gorillas. And so the story goes. Most recently, another molecular technique has come on board—ancient DNA.8 It turns out that the DNA molecule, the molecule that is the molecular gene carrying the information needed to make an organism, is a lot more stable than people had realized. Stunningly, it has proven possible to sequence the genome (the set of genes) of Neanderthals, giving an answer to a question that had intrigued people since before Darwin even. Are we modern humans related to the Neanderthals, in the sense that there were sexual relations between us? Or were they just too ugly that even the most depraved of Homo sapiens drew the line there? Apparently, although not to a great extent, there was significant sexual activity between the groups, with the result that we now carry around 5 percent Neanderthal DNA. Or rather, we of European ancestry now carry around 5 percent Neanderthal DNA. It is not to be found in Asia or in Southern (sub-Sahara) Africa. Who are the cavemen now?
Causes
The talk of Neanderthal DNA starts to push us toward causes, obviously a matter of great interest and equally obviously a matter of much speculation.9 It seems generally agreed that the big event five million or so years ago was the drying up of the lands where the jungles and forests flourished that were our arboreal homes, like those of the other great apes. Our ancestors left the trees and moved out onto the plains. It wasn’t an overnight business. Ardepithecus ramidus lived about a million years before Lucy and although upright was much better at climbing trees than we or she.10 For a long time, hominins lived on the flats and in trees, perhaps using the latter for safety at night. Why there was the move to bipedalism is controversial, and there may not be one simple answer. Plausible suggestions include the benefits of standing upright and thus more easily viewing the surrounding landscape. If the other denizens of the plains or savannahs include carnivores, then knowing about them before they know about us has clear advantages. Also, standing upright minimizes the heat from the sun, no small matter in Africa. And possibly a big advantage was that although we are never going to be able to run that fast absolutely, being bipedal rather than knuckle walkers like the apes means that we could cover large tracts more readily without tiring, thus traveling overall more quickly.
What about the brains?11 General agreement is that the secret here is meat. Without good chunks of high-quality protein, available on a regular basis, there are not going to be big brains. Fussy graduate students would be in trouble. Even if one can live on tofu and lettuce, the natural equivalents of health-food stores were not then on offer. Where then does the protein come from? Obviously, the bodies of other vertebrates. Our ancestors were able to access these bodies and eat them. Note that there was nothing unnatural about this. The great apes supposedly stick to plant foods. I grew up in a family where there was a steady influx of books extolling the virtues of vegetarianism and about how meat eating is unnatural. I am glad to say that the effects of these books were not long-lasting. After a week of fava beans and flatulence, my father would break down at the thought of a pork pie—part of his evolutionary heritage, because claims about the naturalness of vegetarianism were false. The great apes will eat meat—monkeys and the like—if they can get it. They relish it and pity the baby baboon that crosses their path.
How to get the meat? Comparatively, although one would not care to go one-on-one with a silverback gorilla, we hominids (humans and great apes) have never been that strong. At first we were the jackals of the primate world, waiting until carnivores had made their kill and eaten to their desire. Then we could move in and feast. Probably then there was a fairly familiar—and note the word “familiar”—feedback process. There was a selective premium on having the smarts to get bigger chunks than your neighbors, and if cunning and skill were needed, then so be it. Especially if cunning and skill came from having (in Dawkins’s language) a bigger and better on-board computer. So those who did better tended to have offspring more talented than before, and they needed as much if not more meat, and a progression (in a relative sense) was started. Notice though that this could not be something in isolation. One hominin and one lion is not an equal contest. Two hominins and one lion probably isn’t either. But two hominins working together and one lion starts to even things out considerably. In other words, there is a selective premium, not just on cheating lions but on working with your conspecifics. Sociality is at a premium. This would lead to anatomical changes and not just brains. If you are working together and you have deadly weapons—as Americans with their gun fetishes show only too clearly—you are likely to hurt each other. So there is a premium on cutting down on aggressive hormones and dangerous physical features like large canines. And that, of course, makes cooperation even more important. At the same time, with larger brains there is going to be more need of child care and more ability to offer it.
At this point, a particularly important biological principle becomes relevant. Evolutionists distinguish between what they call K-selection and what they call r-selection. In the case of the former, organisms have few offspring but they care for them. In the case of the latter, organisms have many offspring but let them fend for themselves. Elephants and herring. Neither strategy is good in itself, but generally K-selection prevails where conditions are stable and r-selection where unstable. Especially with the latter, you can see how organisms are ready to take advantage in a big way if things are going well. In the case of humans, clearly we were under K-selection pressures and having few offspring for which we cared. Note that, with the coming of intelligence, hominins were increasingly able to control their own environment. Moving into a cave during winter is a good strategy for avoiding the perils of ice and snow. Note also that relatedly, hominins were able to extend their range from Africa out to the rest of the world. General opinion is that this did not come all at once but in waves—the “out of Africa” hypothesis.12 Populations were always in the thousands but sometimes they were quite small—“bottlenecks.” This is thought a reason why Homo sapiens comparatively does not have huge genetic variation, and also why you are going to get separate groups, perhaps even subsets, like Homo sapiens neaderthalensis and Homo sapiens sapiens (us).
Without yet digging into mind and thinking, the really interesting thing about human evolution is that, as I said earlier, it is so familiar in so many ways. For instance, in the past fifty years or so we have learned a huge amount about the evolution of social behavior, at all levels in the animal kingdom, and about how important it is and how natural selection has been so intimately involved all of the time. To take but one example, the American evolutionist David Reznick has ongoing studies of the evolution of guppies, the little fish found (in his case) on the Caribbean island of Trinidad.13 He is particularly interested in such issues as life cycles and why some fish develop very rapidly and come early to maturity and other fish are more leisurely in their development and sexual behavior.14 He ties these sorts of issues into matters to do with predation, habitat, and a host of related features. Organisms at both the social and the physical level do what they can to maximize their reproductive abilities and successes. And these issues involve both natural and sexual selection. If large males are dominating the group, is your best bet to take them on in combat or to take a strategy with a name too vulgar for this book but which involves waiting for opportunities when the leaders are not looking? And how do you do this? If you are top fish, then you can take your time over sex. If you are not, you had better develop adaptations for very efficient quickies.
If the risk of being killed by a predator is high, then natural selection will favor those individuals that devote a larger slice of the pie to reproduction by beginning to have babies when they are younger and making more babies.… Conversely, if predators are scarce or absent and the risk of dying is low, then this long life expectancy shifts the balance in how best to invest resources. The theory then predicts that natural selection will favor those individuals who devoted a smaller slice of pie to reproduction and a bigger slice of pie to their own maintenance. The theory also predicts that they will produce fewer babies and devote more resources to each of them.15
The human story is different, of course. Every story is different. But it is the same sort of story. Think of the frenetic coupling that went on during the First World War when soldiers came home on leave—“hasty weddings” was a phrase that entered the English language. Natural selection (and sexual selection) grabbing the opportunities and molding organisms accordingly. No need for principles unknown or for throwing one’s hands up in defeat.
Purpose?
Return again to the question of purpose and ends in human evolutionary history. I have already expressed my own skepticism on this score, and I am not sure that now with our fleshed-out knowledge of human evolution that I want to change my opinion. The temptation always is to think that with the growth to higher brains we do have progress. The purpose of evolution was to produce beings with large brains, namely, Homo sapiens. Actually, of all people, Gould seems to have been tempted this way once, especially if (as we did above) you tie in the process of brain production with K-selection and r-selection. In his major book Ontogeny and Phylogeny, the work that many (myself included) think is his greatest contribution to scholarship, he writes that he has “tried to link K selection to what we generally regard as ‘progressive’ in evolution, while suggesting that r selection generally serves as a brake upon such evolutionary change. I regard human evolution as a strong confirmation of these views.”16 Which does rather raise the question of why Gould suddenly became so ardent against biological progress. My suspicion (backed by discussions with him) is that it was less epistemological and more political and moral, thinking such progress leads readily to racism with white Europeans at the top and Jews and blacks down the tree. His work The Mismeasure of Man supports this explanation.17
I can say only as I have said before that human evolution isn’t really progressive, at least not in any easy way, and the growth of large brains doesn’t alter things much. Sepkoski with his earthy comment about the virtues of being dumb and the center of the herd puts an end to that kind of thinking. Darwin thought the Scots K-selected and the Irish r-selected and a more general theory of religion suggests that Catholicism promotes r-selection because of the variability of life where it flourishes whereas Protestantism conversely promotes K-selection.18 But neither Irish nor Scots look like they are going extinct, nor do Catholics and Protestants. As always with selection, it depends on the circumstances. In any case, as pointed out, Neanderthals had bigger brains than we. Is evolution now in decline? And what if rather, as in the 1985 novel Galapagos by Kurt Vonnegut, a disease had wiped out Homo sapiens, leaving only isolated Homo floresiensis? Would that disprove progress, for all that the hobbit seems to have been very well adapted to its way of life? Vonnegut, for what it is worth, would have denied this. His survivors turn into seals, and he thinks this a very good thing. Big brains and intelligence are not good adaptations.
Note also that there is good reason to think that human evolution is not yet over and that progress here is going to be relative. One of the most recent and important new adaptive moves was toward lactose tolerance.19 Many adult humans cannot digest milk. Then, with the domestication of cattle, a new and valuable foodstuff became available, and natural selection acted accordingly. Not in every case, of course—the latest hypothesis about Charles Darwin’s long and unexplained illness is that he suffered for this reason.20 But while it was very unpleasant for him, compounded by his wife’s providing meals with huge amounts of cream, lactose tolerance as such is neither good nor bad. In a world without cows, who needs it? It is all relative. From the viewpoint of biology—at least, from the viewpoint of modern Darwinian biology—there is no more progress in human evolution than there is in evolution as a whole. And that, for some of us, is a rather comforting note on which to end this chapter. Whatever purposes we are about to find for human beings, they must be such as acknowledge our oneness with the rest of nature. Value for one is value for all. My dogs approve of that conclusion and so do I.