American society has been consumed by a debate over whether Darwin’s theory of evolution is right or not for a long time. Its a shame for two reasons: its obviously basically right (if you don’t think so, please take some time to study it — its hard to refute) and so many interesting refinements to it have been made that are getting lost in this basic debate. Most people don’t really know how far the theory has come and so haven’t been able to adjust their thinking accordingly, even if they’re willing and able. And that’s a shame, because many recent discoveries put the lie to some of the biggest myths about human evolution.

We’re seeing a bit of a course correction recently. The New York Times, among others, made a big deal about David Quamen’s new book, The Tangled Tree. I haven’t read it, but judging by several reviews I’ve read, the ideas are contemporary, but not new. The basic idea is that we now know that evolution is not a simple binary process. Yes, new species with new, more advantageous traits emerge from old ones in a tree-like fashion.

But as a new study in Science details in depth, related species often interbreed, passing traits back and forth for extended periods of time. The idea that the new kid on the block drives out all the others just doesn’t hold water, in this case.

The article details extensive genomic analysis of hundreds of species of cichlid fish in Lake Victoria. Its a complex tale. The lake is fed by two large river systems, the Congo and the Upper Nile. The fish live in both the rivers and the lake. About 130,000 years ago, fish traveled back and forth from one river to the lake to the other. Than the lake dried up and the fish in each river evolved separately. About 15,000 years ago, they re-united in the once again full lake and began cross-breeding again. In only 15,000 years, these hybridized fish blossomed into about 450 species. Some are small, some are large, some carnivores, some scavengers, some herbivores. The diversity is too great to have occurred solely or even mainly through mutation. If different kinds of cichlids hadn’t interbred to create still more kinds, there would be far fewer kinds, occupying far fewer ecological niches.

Of course, we now know that we humans did something similar, if less spectacular. Up until about 30,000 years ago, we occasionally interbred with Neanderthals and Denisovan hominins (the term for human-like primates), both of whom we share a common ancestor with several hundred thousand years ago.

Some scientists believe that we inherited certain genes for immunity from Neanderthals that helped people survive the many plagues that ravished medieval Asia and Europe. Some of those same genes may be responsible for the small percentage of humans who seem largely immune to HIV. Most Europeans and Asians alive today have at least 1% of their genes from either of the two pre-homo sapien hominins. And this also puts into serious doubt the notion that Neanderthals went extinct because were in some grand competition and we won and they lost. Something more subtle, as yet undetermined, happened.

Very interesting, but so what?

These discoveries show that the 19th century, social Darwinist notion that evolution is a winner-take-all, fight-to-the-death contest may sometimes be true, but is probably more the exception than the rule. Darwin published his work right in the middle of the great expansion of capitalism as an industrial force. Many of his interpreters saw his work in the same light as the economic competitions of the day.

Humans became the ultimate industrialists, the J.P. Morgans of the animal kingdom. Within the human race, there must be winners and losers as well, indelibly stamped in our genetic makeup. This, of course, was a thinly veiled attempt to put a scientific cast on the already existing racist and colonialist views that were common then (and still are today).

Anyone who has spent time in the business world knows that “survival of the fittest” is a powerful idea in the business culture, and the business culture has an outsized influence on society as a whole. “Survival” in this context means one side dominates, the other is absorbed or disappears. “Fittest” means bigger, stronger, faster.

Biologists have established that, for the most part, the route to success for any organism is not to out-compete other species, but to find empty ecological niches that they can fill. That’s a very anthropomorphic way to say that but the idea is that if an organism evolves so that it can eat something or breed somewhere that no other organism cares that much about, it’s more likely to succeed than by having to constantly defend it’s turf.

What modern science also tells us is that the surest way to long-term success is diversity. No species can survive for long with a single monolithic set of traits. Climate changes, food supply changes, and many other things that impact survival change as well. At any given moment, humans as a group need to be a kind of library of traits. When the change comes, those with the newly advantageous traits will prosper, those with the now disadvantageous ones will not.

The picture that’s emerging is that a species wants to have at least some percentage of individuals who are not optimized for the moment but can still survive under a variety of different conditions that may become more common in the future. Today, for example, many species are having to adapt to new temperature, moisture and food supply conditions. Many cannot, but some species retain some individuals who have characteristics descended from warmer eras in the past, before the Ice Ages. Or at least have evolved mechanisms to regulate various processes to morph themselves to respond to these changes.

It’s still true that Darwin’s original idea of random mutations selected by nature is a major determinant of evolution. If anything, the last 50 years of genetics has shown that some mutations (in so-called regulatory genes) have far-reaching implications, causing new limbs to sprout, or body size to increase dramatically. But even that picture is now known to be incomplete. We don’t yet know how much the relative contribution of mutation versus hybridization is, nor how much diversity is enough or too much. But its time to bury the old 19th century notion of nature as some grand cutthroat competition.

What I hope will take its place is a recognition that many of the traits that don’t help people become billionaires are valuable to human society. I don’t argue that we don’t need aggressive, self-interested people, just that we don’t all need to be that way. Without people who excel at empathy, collaboration, self-sacrifice, a willingness to share valuable knowledge and things, we wouldn’t have made it this far. We won’t make it much further if we don’t value them more.

Many ideas in Replay Earth stem from asking what it is that evolution has built for us from our mammalian past. Thinking of humans as animals is always tricky business — we have so many biases and prejudices that meet at that intersection. Nonetheless, we are mammals and we do retain many characteristics of them.

Here’s the ones that intrigued me, and that I wanted to play with in the novel:

1. We are social animals. Most mammals live in a web of families, bands and herds. From what I know of anthropology, prior to the advent of civilization based on formal agriculture about 10,000 years ago, we lived in small groups of dozens, perhaps associated in larger groups of maybe 200. There’s also evidence that in the last 80,000 years or so, maybe multiple such groups in a region might meet up a few times a year to trade and perhaps dance, sing and mate.
2. We, like other mammals, balance competition and collaboration. Our society is highly competitive and that tends to make us look back at see that we were always competitive and emphasize that part of our selves. But we also have always been collaborative, and many anthropologists point to that as equally, or more, responsible for our long-term survival and emergence as one of the planet’s dominant life forms.
3. We think of ourselves as “conscious beings” but like all mammals, we have a powerful set of instinctive responses. Some are learned in childhood, some by experience, and perhaps some are also innate. We have only recently begun to understand that these responses — instinct, the unconscious, subconscious, call it what you will — are not always reined in or controlled by our rational mind. We’re still working all that out, eh?

I continue to read and learn about all of this. Advances in genetics, imaging and so on are helping to clarify the neural picture. Nascent fields like behavioral economics are chipping away at what it means in practice. All good stuff — but I think we are so far away from any firm understanding of how all of that plays out that imagination is entirely called for at this point.