According to a new study led by researchers at The University of Texas at Austin that looked at 10 species of vertebrates, evolution used a kind of universal formula for turning non-monogamous species into monogamous species — turning up the activity of some genes and turning down others in the brain.
“Our study spans 450 million years of evolution, which is how long ago all these species shared a common ancestor,” said Rebecca Young, research associate in UT Austin’s Department of Integrative Biology and first author of the study published today in the journal Proceedings of the National Academy of Sciences.
The authors define monogamy in animals as forming a pair bond with one mate for at least one mating season, sharing at least some of the work of raising offspring and defending young together from predators and other hazards. Researchers still consider animals monogamous if they occasionally mate with another.
The researchers studied five pairs of closely related species — four mammals, two birds, two frogs and two fish — each with one monogamous and one non-monogamous member. These five pairs represent five times in the evolution of vertebrates that monogamy independently arose, such as when the non-monogamous meadow voles and their close relatives the monogamous prairie voles diverged into two separate species.
The researchers compared gene expression in male brains of all 10 species to determine what changes occurred in each of the evolutionary transitions linked to the closely related animals. Despite the complexity of monogamy as a behavior, they found that the same changes in gene expression occurred each time. The finding suggests a level of order in how complex social behaviors come about through the way that genes are expressed in the brain.
This study covers a broader span of evolutionary time than had been explored previously. Other studies have looked at genetic differences related to evolutionary transitions to new traits, but they typically focus on animals separated by, at most, tens of millions of years of evolution, as opposed to the hundreds of millions of years examined with this study.
“Most people wouldn’t expect that across 450 million years, transitions to such complex behaviors would happen the same way every time,” Young said. Paper. (paywall) – Rebecca L. Young, Michael H. Ferkin, Nina F. Ockendon-Powell, Veronica N. Orr, Steven M. Phelps, Ákos Pogány, Corinne L. Richards-Zawacki, Kyle Summers, Tamás Székely, Brian C. Trainor, Araxi O. Urrutia, Gergely Zachar, Lauren A. O’Connell, Hans A. Hofmann. Conserved transcriptomic profiles underpin monogamy across vertebrates. Proceedings of the National Academy of Sciences, 2019; 201813775 DOI: 10.1073/pnas.1813775116
This figure from the University of Texas at Austin demonstrates that “At least five times during the past 450 million years, evolution used a kind of universal formula for turning animals monogamous — turning up the activity of some genes (red) and turning down others (blue) in the brain”:
Notice the odd choice of language: What if, instead of saying “evolution used a kind of universal formula for turning non-monogamous species into monogamous species,” they had said “God used a kind of universal formula for turning non-monogamous species into monogamous species”? Does that formula bother you? Why?
Suppose they had just said, “It appears that there is a standard genetic formula for turning non-monogamous species into monogamous species”? Would that bother you too? Why? Because putting it that way makes you wonder about design but saying “evolution used” precludes the thought? If so, Big Brother smiles on you, you dumb cluck. Better find out what else he’s up to these days.
Seriously, the third way of expressing it would be the least value-laden.
Anyway, a friend writes to say, in response to: “Most people wouldn’t expect that across 450 million years, transitions to such complex behaviors would happen the same way every time”: That’s what you would expect if it’s not common descent but common design.
Incidentally, if humans have that coding, what becomes of claims that monogamy isn’t natural to us? Maybe genetic determinism won’t be as popular then.
See also: STDs + Stone Age = Monogamy!!
“Two Simulations Reach Opposing Conclusions About Why Monogamy Evolved In Primates”
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