genetic essentialism

The Internet has recently brought forth some news about research on  so-called "obesity genes".

Obesity is an increasing problem (no pun intended, of course).  Why it occurs and how it might be mitigated are hot topics in medical science.  One such area of research concerns the genetic contribution to obesity.  Is there an obesity gene or genes and, if so, what might be done about it?

A Wired article gives an account of some research on the matter of how many species of giraffes there are.  Up until now, biologists held that there exists one species, Giraffa camelopardalis, divided into nine subspecies.