Sperm are selfish – and so are we

Selfishness is an uncomfortably common biological phenomenon. Recent research showing how genetic mutations accumulate in sperm in middle and old age underscores this. Stem cells that emerge over time make it much more likely that sperm will have disease-causing mutations in older fathers — perhaps as many as 5 percent of gametes by age 70, the study found.

This discovery goes further than demonstrating the benefits of having younger children. Mutated stem cells do not care whether their deviations cause problems in potential offspring, as long as their cellular progeny make it to the next generation. This is a great example of how the selfish gene remains the evolutionary model we should collectively converge toward. Genes do not act to benefit anything other than themselves. And no matter how many times some people try to defend a “survival of the fittest” view of biology, the explanations must always come back to genetic selection.

The broader debate is old and tired, and hinges on whether you want to believe that evolution via natural selection favors cooperation and friendliness or competitiveness and a cold, calculating organism designed to reproduce successfully at all costs. Over the past century or so, many biologists have characterized these contrasting views as group evolution versus individual selection. The difference between them is fundamental to how we perceive the natural world – and each other.

The divide between the two points of view has always manifested itself across ideological lines. Early ethologists believed that organisms acted for the good of the species. If I survive, according to this view, it is good for everyone, because there will be another person who can at least potentially contribute to the perpetuation of Homo sapiens. Helping each other is an obvious way to achieve this common goal.

The problem—as almost every great biologist has pointed out, from Ronald Fisher, who combined the theories of Charles Darwin with genetics, to modern writers like Richard Dawkins—is that organisms that accept help without providing it to others will always be more successful in the game of life. Individuals who subvert their group are best positioned to succeed – assuming the damage they cause is not so horrific that it kills everyone else in the group.

The individual’s optimum, from an evolutionary point of view, is then to promote cooperation between others while refusing to cooperate himself – and ideally, without anyone knowing. Cooperation, rather than leading to selection for pleasant and useful qualities, simply creates an environment in which competition or exploitation is more effective when undetected.

The problem of subversion undermines groups, whether gametes, bacteria, animals, or people. The stem cell that reproduces at the expense of the organism’s offspring does not know whether its success will harm future generations. The good of the host, let alone the host species, does not matter.

The same goes for human societies, ancient or modern. Those in power – globally, these are often older men – monopolize groups as best they can and often choose younger women themselves. Given the negative consequences of older men remaining reproductively active, as evidenced by new sperm research, it is difficult to understand how anyone can take the group selection model seriously.

But most importantly, these uncomfortable truths about our biological heritage need not define how we behave today. Caring is something we should aim for, not take for granted – and recognizing our selfish heritage, at every biological step down to our genes, is the first step to overcoming it.

Jonathan R. Goodman is the author of Invisible Rivals: How we evolved to compete in a cooperative world