Conclusions: What the Fossils Told Us in Their Own Words
Over the past couple of months, we have talked to the fossils and their surviving descendants. We were guided by a simple question offered by Michael Behe in Darwin's Black Box: "How, exactly?" We asked them what exact mechanisms they used.
We are suspicious of a theory in search of evidence, which is pretty much what Darwinian natural and sexual selection are. We are constantly hearing about a piece of evidence that proves the theory, yet end up in more conundrums than ever.
How much evidence is needed to establish a theory? On how little evidence can the theory survive? How much contradictory evidence is needed for it to crumble? When a theory is as much a cultural as a scientific artifact -- true of all things Darwin -- it is nearly impossible to reach agreement on these questions.
So we listened to many fossils and their surviving descendants to see what they had to say about themselves. We avoided endless renditions of the fan chant for Darwin; we wanted to hear the story in their own words.
What did they tell us? Many different things.
Some told us that they were following an elaborate pattern used by many life forms. But they quickly added that they were not related to the other life forms that also use that pattern (convergent evolution) and could not account for the similarities in their histories.
Some said that they were using many genes they had not inherited; they borrowed them from a variety of unrelated life forms, keeping the useful ones (horizontal gene transfer). They usually employed bacteria to transfer genetic assets. One animal, a sea slug -- Elysia chlorotica (pictured above) -- boasted of stealing the entire apparatus of photosynthesis from a plant, to cope with occasional food shortages (kleptoplasty).
Others explained that they had acquired genetic changes only recently, due to traumatic events in their grandparents' lives (epigenetic change). For decades, these stories were doubted or derided. But gene mapping provided support for many of them. The new technology showed that genes may be inherited in the "On" or "Off" position, and it makes a big difference which. It is not clear in most cases whether the genes will later switch back to a former position, but in any event, the changed form was inherited.
Another group resolved on getting back to the simple life. Instead of doing more than their ancestors, they did less. They ditched many genetic possessions, and found life easier.
Some of the respondents had employed genome doubling, jumping genes, hybridization, and symbiosis, in the business of staying alive and passing life on, though in an altered form.
A surprisingly large group had just not evolved at all, for many millions of years, despite dramatic changes in their environment -- and did not seem any the worse for it.
At the end of our discussion, a question remains. Is there a pattern in all this?
One striking fact is that life forms strive to stay in existence. Consider the sheer variety of strategies employed in just about any location on, in, or above earth. Living things seem to have a level of intentionality. The life forms whose adaptations are the most extreme are called are called extremophiles.
Intentionality should warn us away from too-simple explanations of life forms' history or behavior. The laws or patterns we find will not resemble those of physics because they cannot. Boulders, after all, do not have intentionality. They do not seek to avoid becoming sand.
We did note two patterns:
Larger size and growing complexity (partly a function of multicellular body plans). Over the last 542 million years, marine animals' mean size has increased by 150 times. As it happens, the largest animal that has ever lived, so far as we know, is today's blue whale.
But we should keep in mind that most organisms remained small. There is no general natural law that drives increasing size. But there is room for research on the factors associated with exponential increases in size. What benefit do they provide?
And, as for complexity:
We see a pattern of increasing complexity in the history of life, but that pattern requires some qualification: There were complex creatures in the Cambrian (cf Anomalocaris). Although there is a great variety of complex life forms today, there is a great variety of simpler ones too. They are much more numerous. Humans, by far the most complex life form, are very late arrivals--but we are unique. So it is not clear that there is a natural law favoring the growth of complexity.
The pattern sounds like a work of intelligence. It is complex, not chaotic. It is clearly a pattern, but it cannot really be expressed as a "law" (see, for example, "Dollo's law" for an unsuccessful effort to turn a pattern into a law).
Setting aside the question of intelligence and information for a moment, we might want to revisit a critical change that has crept up on us in the last few decades. The more we learn about the history of life on earth, the less evolution is theory and the more it is history. It is less like Epicureanism and more like World War II. That cannot be good for Darwinian thinking, which fills in large gaps in history by the exercise of theory. Things that "must have" happened if the theory is correct are assumed to have happened.
But history is not like that. Consider, for example, Pearl Harbor, when the Japanese crippled the U.S. Pacific fleet in a surprise attack, though the United States was not at war with Japan. Assume that the account broke off there. Maybe a theory can fill in the blanks for us and tell us what "had to" happen.
But then, what if we later discover more and more evidence for what actually happened? It will be bad news Tuesday for some theories developed in the absence of evidence -- maybe for quite a few theories.
That's a key reason that the hegemony of Darwin is weakening. So much that we now know either doesn't fit the theory or could get on just fine without it.
Another victim may be the culture war around common ancestry. Common ancestry was at one time mainly a religious dispute. Everyone thinks they know what happened at the iconic Scopes "Monkey" Trial (they don't, actually).
But now, since genome mapping became routine, the unthinkable has happened: Actual genomes do not demonstrate the Tree of Life in the neat and orderly way that underlies Darwinian accounts of evolution. They could hardly be expected to do so, given the creativity many life forms exhibit with their own genes via natural genetic engineering, horizontal gene transfer, epigenetics, and a crowd of other mechanisms. The Tree of Life has become a bush or a circle of life.
Finally, when we add up all the demonstrable mechanisms of change in life forms over time, a great deal of the picture is still missing. Either there are many more mechanisms still to be discovered or there is a fundamental force we are not accounting for.
Part of the answer probably lies in the application of information theory to the history of life. On that score, see The Information Enigma.
Much of historical biology has been an effort to rule out the role of intelligence in nature by providing a naturalist account of the origin of information (natural selection acting on random mutations produces information via the simple fact of differing survival rates). Few asked whether that was possible. It was assumed to be true because Darwinian evolution was the only kind assumed to occur. Indeed, it was considered the single greatest idea ever invented, and the only known theory in principle capable of explaining certain aspects of life (p. 287, Blind Watchmaker, 1986). Not any more.
Applying information theory will probably make things worse for Darwinism, by ruling out proposed natural (intelligence-free) paths that exceed the probability resources of the history of the universe. It will, of course, be no threat to accounts of evolution based on mechanisms observed in nature, such as horizontal gene transfer or jumping genes. It may even shed some light on them.
Perhaps the most significant change has been moving the whole debate from the metaphysical realm (did God do it?) to the evidence-based realm (what exactly happened and how shall we interpret it?).
Or, as the fossils said, please do not preach to us any more. Listen to us.
Photo: Elysia chlorotica, by Patrick Krug via Marine Biological Laboratory.
See the rest of the series to date at "Talk to the Fossils: Let's See What They Say Back."