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The Q? Blog

What Does Mate Choice Have to Do with Extinction?

by Devin Reese -- Jan 23, 2017

Devin is the lead digital science writer for the Q?rius website. She writes and gathers media for the Smithsonian Science How? webcast series,...

Can you see any differences between these millimeter-long male and female ostracodes (tiny ocean animals)? Microscope photos of fossil ostracodes by Gene Hunt, Smithsonian.
Can you see any differences between these millimeter-long male and female ostracodes (tiny ocean animals)? Microscope photos of fossil ostracodes by Gene Hunt, Smithsonian.

In the animal kingdom, sexual reproduction is the rule, even for tiny ocean animals such as ostracodes. With just a few exceptions to the rule, male sex cells must fertilize female sex cells to make offspring. While some animals, such as male and female clams, release sex cells into the water for chance encounters, reproduction in many animals requires that males and females find each other.  

Attracting individuals of the same species is achieved in a startling variety of ways that make creative use of the senses, ranging from singing by frogs to dancing by jumping spiders to luminescing by deep-sea animals. Once found, a potential mate may need to be convinced to go forward with the mating relationship. Generally, it's the male doing the convincing because females usually make the larger investment in creating and raising offspring, and so are choosier about who to mate with. 

Let’s take birds as an example. In birds, males invite females to their territories by singing, sporting bright feathers, and doing courtship dances. The more flamboyant males tend to be more successful at attracting females, driving a sort of evolutionary arms race to have the showiest feather plumage. Showier plumage may lead to more mating opportunities, which leads to more offspring, which perpetuates showier plumage in the population of birds.

This form of natural selection driven by mate choice is called “sexual selection.” While it has inspired spectacular characteristics in animals, from feathers to antlers to lion manes, it might have a dark side. Peacocks with larger tails may be easier for wild dogs to catch, elks with larger antlers might not be as agile against wolf attacks, and a lit-up squid might attract a hungry fish instead of a mate. Species with more extreme differences between males and females (“sexual dimorphism”) might be more susceptible to extinction in the long run. 

Smithsonian paleontologist Dr. Gene Hunt is using tiny ocean ostracodes as a model to examine the hypothesis that sexual selection plays a role in extinction. Learn more about what his studies of ostracodes are revealing in a live "Smithsonian Science How" webcast on Thursday, February 9, 2017. In What Tiny Marine Fossils Reveal about Extinction (airs at 11 a.m. and 2 p.m. EST on the Q?rius website), Gene will show you how he tests hypotheses while answering your questions live. You can also get teaching resources to use with the webcast.