By "sex," evolutionary biologists mean genetic mixing between two individuals that results in offspring that are genetically different from each other and from their parents.
In contrast, STRUCTURE analysis showed that individuals sampled on Fernandina and Isabela are genetically similar, with populations on both islands showing a high degree of genetic mixing.
"There's still a lot of genetic mixing," Warren said.
But scientists weren't sure when all this traveling, and genetic mixing, began.
Hybrids, Kronforst said, are a vehicle for the genetic mixing of parent populations.
The genetic mixing work has implications for how today's endangered animals should be protected, Dr. Barlow said.
This, the researchers write in Nature, is evidence that the creatures somehow stay in touch enough to allow for genetic mixing.
There was no evidence of the use of contraceptives or fertility drugs among the women, nor of any genetic mixing with people of African origin, who have higher twinning rates than caucasians, Dr. Matte said.
Wondering whether their results were a fluke, the team then compared the cave bear genome to that of seven other brown bears — one ancient and six modern — and found the same genetic mixing.
He wondered whether animals that have DNA from other species should be preferentially conserved because they are likely to be hardier, or whether biologists should preferentially protect "purer" animals with less genetic mixing.
Dispersal is the movement of individuals from a source, and is a key to genetic mixing and colonization of vacant patches.
