Introgression

Introgression is when genes (pieces of information) from one species move into the genes of another species. To understand introgression, it can be helpful to think of it like playing a game of tag. Let’s say that two groups of kids are playing tag in a park. They could all be wearing the same t-shirts, but one group is wearing red shirts while the other group is wearing blue shirts. Now let’s say that one of the kids in the blue group (we’ll call him “Blue”) runs over to the red group and tags one of them (we’ll call him “Red”). Red, in turn, jumps over to the blue group and tags Blue. What has just happened is that the gene for red t-shirts has been transferred from Red to Blue, and the gene for blue t-shirts has been transferred from Blue to Red. That is exactly like introgression - a gene from one species has been transferred to another species.