Academic journal article The Science Teacher

Solving a Mystery of Evolution

Academic journal article The Science Teacher

Solving a Mystery of Evolution

Article excerpt

Why do some animals have extravagant, showy ornaments--think elk and deer antlers, peacock feathers, and horns on dung beetles--that can be a liability to survival? Charles Darwin couldn't figure it out, but now a Northwestern University research team has a possible explanation for this puzzling phenomenon of evolution.

The researchers developed a mathematical model that made a surprising prediction: In animals with ornamentation, males will evolve out of the tension between natural selection and sexual selection into two distinct subspecies, one with flashy, "costly" ornaments for attracting mates and one with subdued, "low-cost" ornaments.

"Ornamentation does persist in nature, and our quantitative model reveals that a species can split into two subspecies as a result of the ornamentation battle that occurs over time," said Daniel Abrams, an associate professor at the university.

Evidence from nature agrees. The researchers studied available data on animal ornaments, such as deer antlers, peacock feathers, brightness of certain fish, and tail length of some birds, from 15 species. They found the same distribution pattern of ornament sizes across many of the species: The animals often split into the two subgroups predicted by the model, one showy and one subdued, with very few in the middle. …

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