Genetics isn’t as important as once thought for the evolution of altruistic social behavior in some organisms, a new insight into a decade-long debate.
This is the first empirical evidence that suggests social behavior in eusocial species — organisms that are highly organized, with divisions of infertile workers — is only mildly attributed to how related these organisms are to each other.
In evolutionary biology, fitness refers to an organism’s reproductive success and propagation of its genes. When researchers at Hokkaido University studied the foraging and nesting behaviors of the eusocial species Lasioglossum baleicum, commonly known as the sweat bee, they found that the fitness was more a result of the bees’ cooperative behaviour than it was a result of their genetic similarity.
This evidence is contrary to earlier theories that attributed altruistic selfless behavior in eusocial species to genetic relatedness and a want to ensure the propagation of their genes. In some insect species, genetic similarity is higher between sisters than between a sister and its own offspring, and this has been considered the key driver to the formation of a eusociety.
Individual females in social nests are known to have higher fitness than solitary females, meaning that social bees are more successful in propagating their genes. The team has found that 92% of the increase in fitness can be attributed to the benefit of grouping — efficient foraging and defense — while the rest is due to the genetic similarity between the individuals.
The findings indicate that, contrary to previous theories, the main contributing aspect of fitness in a social nest comes from the benefit of grouping. “There has been a decade-long debate among scientists as to whether genetic similarity or the benefit of grouping is the primary drive of sociality. Our study could help reveal some of the factors behind the evolution of cooperation, including among humans, by quantifying how much cooperative behavior contributes to the increased fitness of altruistic individuals in a group,” says Hasegawa. Paper. (open access) – Yusaku Ohkubo, Tatsuhiro Yamamoto, Natsuki Ogusu, Saori Watanabe, Yuuka Murakami, Norihiro Yagi, Eisuke Hasegawa. The benefits of grouping as a main driver of social evolution in a halictine bee. Science Advances, 2018; 4 (10): e1700741 DOI: 10.1126/sciadv.1700741 More.
The authors don’t quite spell it out but this is a blow to “selfish gene” thinking, according to which the evolution of co-operation is explained by the fact that the co-operators are more closely related to each other (selfish genes somehow “want to” pass themselves on and thus “select” these situations (Darwinian natural selection).
The researchers find, rather, that the benefit of co-operation is better survival rates (presumably for all the genes involved) due to reduced risk of predation.
Note, by the way, that the same word, “altruism,” typically refers both to human philanthropy (which is usually unrelated to concerns about the survival of one’s genes) and the organization of insect colonies. Take about a mechanism for turning nonsense into science, using nothing but a little twist of the ol’ Darwin.
See also: Claim: Our brains are hardwired for altruism
Neuroscience News: Are humans hardwired for transgressions?
Betrayals helped humans spread
An evolutionary challenge: explaining away compassion, philanthropy, and self-sacrifice
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