The Arrow of Evolution

Most evolutionary biologists would agree with the contention that evolution has no long-term direction.

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Most evolutionary biologists would agree with the contention that evolution has no long-term direction. In other words, evolutionary change is shaped by the contingencies and exigencies of the present set of circumstances, searching blindly through “adaptive space” for local optimal solutions. Just “good-enough.” For now.

In the realm of biology, this is illustrated by various “retrofits” one can see in form and function. The human vertebrate is a notoriously suboptimal feature, but it is the outcome of hundreds of millions of years of prior evolution when our ancestors were primarily quadrupeds. We make upright posture and bipedal locomotion work for us, but there’s a reason that prehistoric bipedal dinosaurs would likely run us down with ease. Jurassic Park isn’t all fantasy.

Upright hominins are utilizing new engineering technology which still has a lot of “bugs.”

Caption upright hominins are utilizing new engineering technology which still has a lot of “bugs.”

Even the classic view of human evolution where short slouching creatures become upright moderns requires a rethinking. The reality is that Homo erectus was probably already as tall, on average, as modern human populations. And until contemporary times the tallest human populations known seem to date from the Pleistocene. Humans have been shrinking since their Paleolithic peak, with the 20th- century spike across the developed world reversing millennia of decline.

If evolution has a goal, oftentimes it looks like it hasn’t made up its mind.

The late paleontologist Stephen Jay Gould made a forceful case for the importance of chance and necessity, randomness, in the diversity of life on earth. In his book A Wonderful Life, he states:

The divine tape recorder holds a million scenarios, each perfectly sensible. Little quirks at the outset, occurring for no particular reason, unleash cascades of consequences that make a particular feature seem inevitable in retrospect. But the slightest early nudge contacts a different groove, and history veers into another plausible channel, diverging continually from its original pathway. The end results are so different, the initial perturbation so apparently trivial.

Gould’s understanding of evolution is at one extreme of the views about the role of randomness, and lack of purposiveness, of natural history. It should not be a surprise that his view is not universally held.

The researcher upon whose work his argument in A Wonderful Life was built, Simon Conway Morris, strongly disagreed with Gould’s interpretation of paleontology and natural history. In a series of books, he outlined the idea that evolution does have a broad directionality due to various forces, such as the necessity of streamlined body-plans for predators in the ocean. The fact that dolphins resemble ancient Mesozoic marine reptiles is obviously not a coincidence and illustrates that rewinding the tape only led to large-bodied land vertebrates converging upon the same body plan to adapt to the oceans.

Caption upright hominins are utilizing new engineering technology which still has a lot of “bugs.”

Richard Dawkins reiterates this argument in
 The Ancestor’s Tale. Dawkins also observes 
that over the billions of years that life has 
been present on earth, there seems to be a 
gradual, if sometimes halting, progression 
toward greater complexity. Most of our 
planet’s history was dominated by 
cyanobacteria and other prokaryotes, but 
more recently multicellular life forms have 
emerged to make up a much greater 
proportion of the biomass and dominate 
ecosystems. Despite mass extinctions such as the one at the end of the Permian or the event that resulted in the extinction of dinosaurs 60 million years ago, multicellular life is here to stay.

Now, over the last several million years humans have been expanding across the face of the earth and reshaping the landscape. While it is easy to dismiss humans as just another medium-sized megafauna, today we and our domesticates account for 96 percent of the mammalian biomass on planet earth!

This is amazing in light of the fact that tens of thousands of years ago it seems likely that our species numbered in the tens of thousands. Today we number in the billions. It is just our luck and happenstance?

Caption upright hominins are utilizing new engineering technology which still has a lot of “bugs.”

Humans are wont to perceive themselves as the pinnacle for creation, so scientists are cautious and skeptical of presuming we are in fact something special. Much of modern science has been involved in the project of showing just how banal our place in the universe is. An extension of the Copernican project, which rejected the old idea that the earth was the center of the universe.

We’re on the edge of a spiral galaxy, on a small planet circling a modest G-class star. Our species has been present on this planet for a tiny fraction of its existence of 4 billion years. What are we in the grand scheme of things?

And yet, it is quite likely that we are the first intelligent species on this planet capable of exploiting its mineral resources, judging by the fact that there were so many exploitable surface deposits of coal and iron during our own industrialization. The emergence of humans was also likely a final push in the extinction of numerous megafauna at the end of the Pleistocene, which had persisted through many interglacials.

Humans were the first large placental mammal to arrive in Australia and New Zealand, eventually bringing a host of others in their wake. No other large mammal seems to have been able to occupy six of the seven continents before our own species. And this feat was achieved 15,000 years ago when we were small hunter-gatherer bands.

Today, the entire biogeography of the planet has been resculpted by us, from red deer in New Zealand to European earthworms in North America.

This is then the “Anthropocene.” An age when humanity holds the leash on the planet’s biosphere and engages in endeavors which will change the future of the planet, or endanger it….

The pessimistic outcomes for the planet due to the evolution of humans, an intelligent, social, and technological, species have been well aired. But what about the optimistic ones?

There are some thinkers who have long argued that evolution on this planet was almost certainly at some point going to produce intelligent technological life. The “encephalization” of large animals on this planet, the relative size of the brain in relation to the body, had been gradually increasing long before the emergence of the hominin lineage, which is well known to be defined by very large brains.

In the 1950s a Catholic priest and paleontologist named Pierre Teilhard de Chardin promoted the idea that evolution was driving the universe toward a cosmic consciousness. Most scientists were very skeptical of such teleological thinking. That evolution had some ultimate purpose beyond optimizing local fitness. Some direction toward a final culmination. Today, they still remain very skeptical.

Decades later in the 1990s the science writer Robert Wright wrote Nonzero: The Logic of Human Destiny. In it, he argued that evolutionary processes were leading up to humans and that our species was advancing through “non-zero sum” interactions. We had broken the grip of Malthus and the standard carrying capacity charts of ecologists through cultural innovation.

Today, David Sloan Wilson, a mainstream evolutionary biologist, argues that selection pressures on human groups may have driven increases in altruism and prosocial behavior to such an extent that he now imagines that successful completion of the Darwinian project may lead exactly to some sort of global consciousness, as envisaged by de Chardin. A mind which is able to optimize fitness at the level of the whole planet.

Of course, even David Sloan Wilson is not speaking in terms of inevitabilities. The Anthropocene is a dangerous time for the long-term time horizon of the planet’s ecosystems. The evolution of modern humans and their cultural creativity has unleashed a Pandora’s box of problems. But Wilson and his fellow-travelers seem to be suggesting that this is not just chance and necessity. That the earth has two possible final outcomes, one dire, and one nearly utopian.

And remember, opening Pandora’s box also unleashed “hope” upon the world.

Bob, Researcher
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