by Erin Anderson, editor
Chris Darimont ’92, an alumnus of SMUS and an award-winning conservation biologist, returned to SMUS to talk about his latest research on humanity’s effects on evolution. In addition to his public talk, Chris dropped in on a few classes.
Currently featured in Maclean’s magazine, Chris’s latest work suggests humanity is causing rapid evolutionary changes in many species. His findings have shown that creatures from fish to rams are changing in size, altering travel patterns, and reproducing earlier in order to adapt to humanity’s presence. Typically, in the wild, a deer or stag that is smaller would be a likely target for a predator, due to their being weaker than the rest of their herd. In contrast, a human hunter would be more likely to target a larger animal, because of both hunting regulations and the desirable size for keepsakes such as antlers.
The way these patterns are impacting evolution, is that the survivors of predation determine which characteristics are passed on – namely, their own. For example, under many current fishing regulations, younger fish must be tossed back, but older ones are allowed to be kept. Thus, fish that reproduce at a younger age are more likely to be able to reproduce before they are caught.
Since humanity is responsible for as much as 80-90 percent of the annual harvest in some animal populations, their impact significantly outweighs that of natural predators, and animals are adapting to make themselves less likely targets for humans. Rams, for example, are producing smaller horns, making them less attractive to hunters. In salmon populations, the spawning fish who head back to breed later in the season are more likely to be caught than those who arrive first, so they are heading back earlier and earlier each year.
Though humanity impacts animal species in a number of ways, such as altering natural environments, Chris’ research shows that the populations that are targeted for predation adapt much more quickly than animals affected in other ways and even faster than animals living in the wild. However, his research also suggests that while animal populations change rapidly in response to this predation, once the predation ceases, animals are slow to rebound.
In general, animals that reproduce at a young age produce much fewer offspring than they would at a more mature age. So, when animals adapt to harvesting by reproducing when they’re younger, they don’t produce as many young, and not only does it take longer for the population to return to its original size, but without the impetus of predation, the population will take even longer to return to its original rate of replenishment.
Because of this, Chris believes that the best way to combat these effects is to alter the size and age of the animals we harvest as well as decrease our harvesting of animals as a whole. His research has also been featured in the Times Colonist and Discover Magazine, which named his work one of the top 100 stories in 2009.