[vneur]

For this to be biological and not cultural we would need to see evidence that this happens before baby/infant primates are old enough to observe their parents performing similar behaviors, or when raised in isolation. The only citation here that matches that is the first one, and even then the experimenter was a part of the experiment and not blinded to infant sex, so there is a major possible source of bias there, and more recent papers appear to contradict this effect [1]. Rather than cite one-off studies from the 2000s this is a situation where a meta-analysis or review would be ideal, but I don't see one in a quick search. If you are aware of one that would be helpful to better understand this claim.

https://www.sciencedirect.com/science/article/pii/S002209651...

[hbbbbvccxdd]

Infants exhibit preferences consistent with their biological sex before they know which sex they are.

Boys raised by single mothers with no male role model do not exhibit unusual female behavior.

The differences between male and female infants are consistent with the well studied effects of sex hormones in adults.

[sandstrom]

I cited the 2000 study because it was the first one doing this type of experiment at a very early age (the babies were 36 hours! old).

No, that's wrong, it was properly blinded:

  The videotapes were coded by two judges who were blind to the infant’s sex, to calculate the number of seconds 
  the infants looked at each stimulus. A second observer (independent of the first pair and also blind 
  to the infants’ sex) was trained to use the same coding technique for 20 randomly selected 
  infants to establish reliability. 

If you want more, here is another one on newborn macaques:

https://www.nature.com/articles/srep19669

Or this one, where adding testosterone to rhesus monkeys causes their female offspring to be "masculinized':

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146061/

[bloqs]

It happens cross culturally which goes most of the way to answering this