Don: Ready, Ya?l?

Ya?l: Yep.

D: Here goes 3.1415 9265 3589 7932 3846 2643 3832 79. Ta da!

Y: Wow, you really can recite pi to the thirtieth decimal place. Very impressive, Don! You must have the memory of an elephant.

D: Thanks, Ya?l, but do elephants really have good memories? Or is that just a saying?

Y: Oh, it's real. In fact, a study on elephant memory shows that having a strong memory   helps elephants survive in the wild.

D: What do you mean?

Y: Well, scientists studying elephants in Tanzania's Tarangire National Park in Africa  knew that some elephants lived through a terrible drought from 1958 to 1961. Now  cut to 1993, when there's a second severe drought. Some elephant groups left the  park, but only those with members who were old enough to have possibly   remembered the earlier drought. The group that stayed in the park was composed of  younger elephants.

D: I see. And I assume that the elephants that left the park in 1993 were better able to  survive.

Y: Right. The elephants that left the park lost only ten- percent of their calves. But the  group that stuck it out lost forty-percent of its young.

D: So in this case, at least, evolution selects for elephants that have memories strong  enough to remember stuff from their childhood.

Y: Yep. For elephants, memory is a survival tool.