To this day, biologists debate about how altruistic behaviors evolve and persist. Sterile ants faithfully tend their queen with no chance of reproducing themselves. Bees lay down their lives to defend the hive. "Why do they do that?" asks University of Vermont biologist Charles Goodnight. "Doesn't natural selection drive animals to behaviors that increase their own chances of survival, not those of others?"
This question underlies the decades-long debate between two camps of scientists. On one side, are those who argue in favor of "kin selection," in which individuals are altruistic to those who share their genes. On the other side, are those who argue in favor of "group selection," (or "multilevel selection") in which altruism arises from being part of a group.
In a recent edition of the journal Nature a team of 18 scientists, including UVM's Goodnight, show that the two traditional approaches are actually mathematically equivalent.
"What we did in this paper was take the equations of a group that was very strongly kin selectionist and we worked through them and translated them back into classic equations," says Goodnight. "and they're the same."
"It is remarkable that kin selection has been widely accepted and group selection widely disparaged," says Michael Wade, a biologist at Indiana University, and the lead author on the paper, "when they are actually equivalent mathematically."
Goodnight's colleague in the UVM biology department, Sara Cahan, agrees with this conclusion. But she doesn't agree with everything in Goodnight's paper — and is more in the kin selection camp. "Charles and I really enjoy one another — I respect Charles very highly — but we do tend to argue a lot," she says, with a laugh. (Perhaps it's no wonder the students she and Goodnight had in their co-taught graduate seminar "Levels of Selection" called the course "Crossfire.")
"This debate is far from over," says Charles Goodnight.