In other words, the development of the individual mirrors that of the species. (Not quite it, but close enough.)
xkcd had a comic a few days ago that floats the theory that from birth to age three or so, people are [non-sentient]. Of course this is nonsensical, which you hopefully know as soon as you've had a kid, but I've heard parents here and there float a similar idea. (Reminds me of how the theory that newborns don't feel pain persists in some circles; once upon a time it was common practice to perform surgeries on neonates sans anesthesia, and circumcisions are still sometimes done with no pain relief.)
In truth, personality is apparent even before birth. We used to call Marie Rabid Weasel because of how active she was, and she has not slowed down one iota since birth. She figured out how to sit on her own and immediately after that rolled over and started trying to crawl. Before she figured out crawling, though, she would throw herself across the bed in an attempt to get to me if I was not within easy reach.
Not too long after she finally figured out how to crawl, she started pulling herself up. She can now, at just shy of seven months, stand on her own for a precarious second or two. As I type this, in fact, she has pulled herself up using my arm about three times; balancing herself slightly using my shoulder, she smiles at me and babbles "Mam mam mam mam mam mam."
The best part of having several children is knowing the general arc their development will take. Mine seem to go two-by-two...Esther tracked Bobbie very closely, and Marie is tracking Linda very closely (seems I chose well in also naming her after my sister). She shares her older sister's absolute fearlessness. She will crawl to the very edge of the bed and lean over with only her hips on the bed to play with things, completely oblivious to the whole "if you fall, it will hurt" thing. (She doesn't much care for being on the floor, though.) At her age, Linda was climbing everything she could come across. So I am wondering whether she will also start walking at a young age. Bobbie and Esther both walked at about 13 months; Linda started walking at 10 months--adjusted for being premature, her developmental age was 9 months--and running at 10.5.
This is my favorite part of life. The mothering thing. It's the only thing I've ever been certain of wanting out of life. I will confess that although I understand not wanting to have children, and even (sort of) understand just having one, but I don't really understand having just two or three. I mean nothing bad by it, though; I'm well aware that most people don't understand having four or more. I am certainly out of the norm in this too. I'll confess to being a wee bit envious of the Duggars, even. There will hopefully be more babies for us in a few years, just not right now.
Until then, I will enjoy watching this baby develop. Knowing how much cuter it gets from here makes it that much better.