Genetically-modified crops might turn into weeds by escaping from farms, or by interbreeding with other species.
The startling decline in wild Scottish salmon is being blamed on pollution and interbreeding between wild and farmed salmon.
ECONOMIST: Pressure is mounting to do something about salmon farms
This lends weight to the theory that a viable hybrid population was sustained by interbreeding over a long time.
Moreover, the argument that the two species were interbreeding over such a long time is, to say the least, controversial.
Also, the team confirm that there was some interbreeding between the now-lost species and the ancestors of some people alive today.
This change could be radical enough to prevent the new strain from interbreeding with the old, signalling the birth of a new species.
Humans and chimpanzees were interbreeding for all this time, before finally separating no more than 6.3m years ago and probably less than 5.4m years ago.
After interbreeding, Africanized strains migrated north, reaching Texas in 1990.
The progeny of interbreeding start with a big evolutionary disadvantage.
To erase the difference between blacks and whites, Saletan wrote, would probably require vigorous interbreeding between the races, or some kind of corrective genetic engineering aimed at upgrading African stock.
The team found that it took at least hundreds of thousands of years and, perhaps, 4m years for human and chimpanzee ancestors to stop interbreeding after they began to be differentiated.
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