"A flaw in his argument of genetic deterioration in intelligence was the widely accepted fact that intelligence as measured by IQ tests has actually increased over the past 50 years."

They live relatively long lives - about 40 years in the case of the African rhinos - which means that any genetic deterioration would take place relatively slowly.

While the other X-Men seemingly split up to deal with personal affairs, Cerebra remains at the ranch, intent on reversing the genetic deterioration of Zhao's "chosen".

It's a problem of genetic deterioration.

As such, they are forced to use technology as a "crutch" for their genetic deterioration.

"rapid genetic deterioration in captive populations:causes and conservation implications."

The butterfly association also raises the concern that interbreeding of otherwise separate populations could cause genetic deterioration of endemic varieties that have adapted to local conditions and warp migratory behaviors.

"Or suffer genetic deterioration."

Aurora says "genetic deterioration".

Currently, there is no evidence of real or potential genetic 'deterioration' due to harvesting, nor any reason to suspect it.