Sex. Many (but not all) animals do it. Partners come together to combine their genetic material in hopes of creating a healthy next generation for passing down their genes.
For humans, romance, love and sometimes Valentine's Day can be involved, although the formula varies greatly depending on culture. Meanwhile, other animals go about it in a dizzying variety of ways.
Creatures may form pair bonds or mate promiscuously, like bonobos. Corals and fish spew their eggs and sperm out into the environment to unite there.
A panel discussion at the New York Academy of Sciences on Tuesday (Feb. 12) explored how lust, and sometimes love, are manifested throughout the animal kingdom, past and present.
First, figure out who's who.
"Sexing," the scientific term for figuring out whether an individual is male or female, has been a challenge for paleontologists studying dinosaurs.
Looking for skeletal differences just didn't work, said panelist Brian Switek, who writes about dinosaurs and is the author of a forthcoming book, "My Beloved Brontosaurus: On the Road with Old Bones, New Science, and Our Favorite Dinosaurs" (Scientific American/FSG).
In recent years, however, the task has become more feasible. For instance, paleontologists have begun looking in fossils for what is called medullary bones.
Among birds, which experts consider to be living dinosaurs, females store calcium for egg-laying in this temporary bone tissue. [Top 10 Swingers of the Animal Kingdom]
Fatherhood can be complicated.
"Thanks to molecular testing, we can now genetically trace, like Maury Povich, who's the daddy," said Danielle Lee, who studies animal behavior and behavioral ecology at Oklahoma State University.
The results of testing: The female's social partner may not be the father of any of her young. Moderator Joshua Ginsberg of the Wildlife Conservation Society pointed out that the same phenomenon applies to humans.
The man on the birth certificate is not always the biological father, although the rates at which this happens vary widely depending on the population.
Marina Cords, a professor at Columbia University who has studied blue monkeys for 30 years, said that the female monkeys who live in harems "seem to get pretty tired of the one guy." She added, "They sneak around, too."
There's more than one way to get the girl.
Not all males within a species are created equal.
Among some animals, such as salmon and squid, some males invest more energy in acquiring the traits attractive to females.
"Others are smaller: the wimpies, if you will," Lee said. These are the "sneaker males," which use their innocuous presence to their advantage to mate furtively with the females.
See the rest of the story at Business Insider