[wittekm]

The article says that the modern peanut has 20 chromosomes, whereas its ancestors each had 10. At least in animal hybridization, the hybrid chromosome amount lies between that of the two parents. So what's up with that? Wikipedia mentions "doubling."

[pluteoid]

As others observed this is a common condition in plants (where repeated hybridizations can result in even higher ploidy conditions, e.g. tetraploid wheat, sexaploid sedums).

But as you ask, why isn't it observed as often in animals, or indeed at all in mammals? One argument is that plants generally feature fewer tissue types, and their anatomy shows less interdependency of parts: they have a body plan of repeated units showing some redundancy. (Cutting off a branch is not like cutting off a leg.)

In other words, by many metrics of organismal complexity, plants are less complex than animals, such that their developmental programmes can "tolerate" relatively major disruptions to genomic organization.

There are some insights in this paper: http://www.ncbi.nlm.nih.gov/pubmed/15780745

[gus_massa]

It's very usual in plants to have a weird number of copies of the chromosomes. I remember a very detailed submission from a few years ago, but I can't find it.

I think that the relevant Wikipedia page is https://en.wikipedia.org/wiki/Polyploid#Plants and https://en.wikipedia.org/wiki/Polyploid#Allopolyploidy .

[GFK_of_xmaspast]

At a guess, peanut is probably tetraploid, with four copies of each gene instead of two. (Polyploidy is common in plants)

[cgriswald]

> (Polyploidy is common in plants)

Especially crops.