The Advantage of Being a Night Owl

The nocturnal sturgeon survived, while the
dinosaurs did not (NYNHP image)

Evolutionary biologists, by using computer modeling, genetics, and datasets that weren't available until recently, theorize that nocturnal behavior helped species avoid extinction.

Researchers already knew that many nocturnal mammals survived the mass extinction that followed an asteroid strike 66 million years ago, whereas the dinosaurs, which were largely diurnal, did not (except for birds). The new study extends that pattern to other catastrophes and other species, including aquatic ones.

But how did researchers know that species that lived millions of years ago were nocturnal (fossils provide very little information)?

Maxwell Shafer, an evolutionary biologist at the University of Toronto, and his colleagues at the University of Basel focused on living fish, which represent half of all vertebrates. They combed the literature to determine the day-night behaviors of almost 4000 bony fish species and 135 cartilaginous ones, such as sharks, and plotted these behaviors on a fish tree of life. Then they carried out many computer simulations of possible day-night activity patterns in the ancestors of modern fish, until they came across the one that best reproduced the day-night patterns of today’s species.

The nocturnal "advantage" may also apply to mammals:

Previous studies had suggested early mammals were nocturnal to avoid dinosaurs. After those predators disappeared, mammals switched to being active during the day. Amphibians and other land vertebrates also tended to be nocturnal throughout much of their evolution, according to other studies, but more and more have become diurnal. Shafer’s team proposes that for all vertebrates, nocturnality was a survival advantage during catastrophes.

Our family is a mixture of night owls and early birds. It's comforting to know that some of us have an improved shot at surviving an extinction-level event.