What is greed other than a way of describing people putting their wants and desires first to an extent we don't approve of?
In my experience there is no limit to how strongly small children put their wants and desires first. Therefore they are, by definition, "greedy". There is no malice in this. There is no awareness of consequences for others. But any adult who acted in the same way would be considered incredibly greedy.
I understand greed as desire to control, posses or consume, even beyond the point where it does you or your environment any good. And on that account infants are already more differentiated in their behaviour. They pursue only as long as it does them good (in most cases).
There are the kids which cling to this one toy car which is suddenly in very high regard among two friends, but there are also those which give it willingly away, once the other child starts crying or only looking very sadly. Compassion over greed. I see that quite often.
So I don't think one can say that in the infant (as a "pure" human, which has not been moderated by social norms) you can see that "humans are greedy." And even less so that holds for adults.
In my experience there is no limit to how strongly small children put their wants and desires first. Therefore they are, by definition, "greedy". There is no malice in this. There is no awareness of consequences for others. But any adult who acted in the same way would be considered incredibly greedy.