[infinite8s]

The 'ma' and 'pa' sounds are some of the easiest sounds to make by babies since they just require the lips and don't involve the tongue.

[talideon]

You might be interested in the article by Larry Trask linked to here: http://languagehat.com/trask-on-mama-and-papa/

[infinite8s]

I'm not sure why I was downvoted - Larry Trask's article has the exact same explanation i gave above - mainly that the 'm' and 'p' sounds are the easiest consonant vocalizations that babies can do.