Actually, evidence for cannibalism in the palaeolithic era is widespread. Some cannibalism can be attributed to eating the dead of the relevant tribe, but other examples are likely due to intertribal warfare which was frequent but intermittent. We see this also in the case of more modern hunter-gatherers who believed customs such as that eating the heart of an enemy would give one the enemy's courage etc.
Probably more widespread in the upper-paleolithic era.
What I see is that it is a cultural practice, more than a natural/ instinctual one, in the cases where food is abundant enough as to not have to rely on human meat to survive.
Infanticide was also heavily practised in palaeolithic times. No doubt because constant migration and the threat of famine would sometimes mean that the parents had to kill and eat their own offspring in order for the two of them to survive.
Yes, perhaps. I mean, other species such as dogs and cat sometime eat their offspring that are the least likely to survive...
Maybe there's less chances of kuru diseases when eating people from the same bloodline.
BTW my dog just gave birth to six healthy puppies last night

we actually talked with the vet about not separating the puppies from their mother too much, or she might end up eating them...
It's even more extreme with cats where only a stroke from a stranger might disrupt the kitten's natural distinctive odor, and lead the mother to reject it, or eat it.