Cooperation and Evolution: The Case of Sympatric Speciation.

I like to keep a tab on current thinking regarding cooperation in biology, especially evolutionary biology.

I do this for two reasons.

Firstly, I find evolutionary biology to be intrinsically fascinating and I am always on the lookout for new types of thinking in evolutionary theory that step beyond the boundaries of standard analysis. I like this because it enriches, indeed deepens, our understanding of evolution.

Secondly, I like to do this because I feel that the advent of a type of crude selfish gene account of evolution in the neoliberal era has been unfortunate, and has been used by ideologues to justify neoliberal policy making. It has even been used to justify a might makes right approach to international relations, which carries with it certain unpleasant historical connotations.

Speciation can be seen as occurring along a spectrum with Mayr’s allopatric speciation, where species evolve from a common ancestor due to the presence of a geographical barrier that prevents gene flow between populations, and sympatric speciation, where species evolve from a single ancestor whilst inhabiting the same geographic region. With sympatric speciation populations diverge even though there exists no barrier to gene flow or interbreeding.

Two key points of controversy regarding sympatric speciation exist, namely what drives it and how frequent is it. Mayr held that natural selection could not explain sympatric speciation, and so therefore did not occur in nature. But we know that it does, so Mayr’s eliminativism does not hold.

The “Darwinian fundamentalist,” competition, adaptation and all that, John Maynard Smith held that sympatric speciation occurs when two population groups occupy differing ecological niches in the same geographic region. One group is more adapted to one niche, and so speciation on standard adaptationist lines occurs.

It is surmised, also, that sympatric speciation is not common.

A news article on sympatric speciation caught my attention. This article reviews a paper by Roberto Cazzolla Gatti that criticises the principle of competitive exclusion, which holds that two species competing for resources cannot stably coexist in the same region as slight advantages of fitness will see one species overwhelm the other over time. This is a type of common sense, as it were, but it is puzzling in a theoretical sense as it is difficult to envision how this principle leads to the rich layers of biodiversity that we observe in nature.

Secondly, we don’t actually see the principle of competitive exclusion at work in nature nearly as pervasively as intuition would have it. The article cites Gatti as stating;

“My model predicts that the coexistence of two species in a sympatric way can happen only if there is low competition or weak competitive exclusion between them and a kind of avoidance of competition that leads to a slight shift of the niche of a meta-population, which accumulated a series phenotypic differences due to genomic inclusions coming from other sources of genes. Thus, eventually, it’s the avoidance of competition and the process that I call endo-geno-symbiosis that drives the expansion of the diversity of living beings.”

Empirical evidence suggests that sympatric speciation is also, it would appear, quite common; the article cites David Marques to this affect;

“We cannot know for sure that the Lake Constance sticklebacks will continue evolving until they become two non-interbreeding species. But evidence for sympatric speciation is growing, from mole rats in Israel to palms on Lord Howe Island, Australia, and apple maggots evolved from hawthorn maggots in North America, leading some evolutionary biologists to think it could be surprisingly common.”

The concept of endo-geno-symbosis, a form of genetic cooperation, is intriguing with respect to a recent book published on the social life of genes.

Pioneers in the nascent field of systems biology, Itai Yanai and Martin Lercher present a compelling new framework to understand how the human genome evolved and why understanding the interactions among our genes shifts the basic paradigm of modern biology. Contrary to what Dawkins’s popular metaphor seems to imply, the genome is not made of individual genes that focus solely on their own survival. Instead, our genomes comprise a society of genes which, like human societies, is composed of members that form alliances and rivalries.

In language accessible to lay readers, The Society of Genes uncovers genetic strategies of cooperation and competition at biological scales ranging from individual cells to entire species. It captures the way the genome works in cancer cells and Neanderthals, in sexual reproduction and the origin of life, always underscoring one critical point: that only by putting the interactions among genes at center stage can we appreciate the logic of life.

At the moment, of course, we are experiencing a significant loss of biodiversity due to human activities or better still a human induced ecological crisis. When biodiversity declines because of the actions of a single species you can probably guess that competition may well be at work. To cite Gatti;

“These theoretical findings, confirmed by empirical approaches, should motivate our species to think before it is too late about how human competition, for the first time in the history of life on Earth, has been systematically leading to the extinction of animals and plants.

This is a point to which I shall return.

One of the puzzles of human evolution concerns not the evolution of Homo sapiens per se, but the all too obvious fact that this rather annoying lump of grey matter, as Bertrand Russell once termed it, remains the only remaining species of the genus Homo. That is to say, why are we the only remaining hominid species?

This lack of biodiversity puzzle may be, to errantly speculate, the result of competition among hominids sharing the African plains. Let us not focus on different hominid species and focus on just one, namely our own. A recent article in New Scientist states

We know that modern humans first arrived in Europe about 45,000 years ago when the continent was still a Neanderthal stronghold. Over the next 30,000 years – archaeological work has revealed – a procession of different cultures, each associated with different artefacts and lifestyles, rose in Europe.

Archaeologists tend to think these sort of cultural shifts reflect the spread of new ideas through an unchanging population. But a new analysis of nuclear DNA taken from 51 ancient Eurasians tells a different story. They actually reflected the spread of different peoples.

Now that’s hardly an example of “sympatric culturation.”

To return to the themes that opened this post. Humanity’s relationship with nature is mediated through social structure. Ours is a social system, both in its political and economic aspects, that has competition at its core and this is accompanied by systems of ideology that celebrate the virtues of competition.

There appear to be ecological limits to competition and ours may well be a species that is starting to hit those limits. A competitive economic system that has no regard for ecology cannot endure, and a competitive system of states that ultimately relies upon nuclear deterrence for its stability is also fraught with danger.

Work on cooperation in evolution is worth thinking about, and keeping an eye out for, as it tends to undermine systems of ideology that celebrate competition.