Computer scientist David Ackley has a good explanation by example:
"Suppose you have a population of squirrels that way back in the foggy
past learned to jump from tree to tree. One population might learn to do
this and another population doesn't. The population that learned
tree-jumping will get evolutionarily rewarded for things that help the
task, like developing webbing between the toes, while the other
population won't get rewarded for that. So looking at this over
evolutionary time, you can now see that the population that used to
learn to jump from tree to tree becomes _born_ to jump from tree to
tree. What the ancestors learned, the decendants inherited. It's like
Lamarkian evolution, except it's not in fact Lamarkian."
This might have some bearing on both the discusions of aquatic apes
vs predators and competing memes.