Hence me giving a range of 6-9 months. My niece was walking not long after 9 months, it's rare but not unheard of. A newborn baby simply wouldn't have the physical strength or rigidity, though.

Earliest I've seen was 9/10 months, that kid looked so strange to me, they could barely hold their head up as they tottered around like a drunk. I wonder if the parents promoted early walking?

People do that successfully, the problem is that if babies skip the crawling phase then it may cause learning disabilities among other things. Which is fascinating in the context of this conversation. The order in which things are learned can be very critical!

Yes, successful crawlers might walk later, kids that learn to bum-shuffle (propel forwards whilst sitting on their bottoms) might not crawl much.

Our eldest wasn't interested in crawling really and went almost straight to walking but not until about 14 months IIRC (it was > 10 years back).

We did baby sign (a sort of simplified BSL; would recommend) and some people suggested it would retard speech - same child modified a sign before 12 months and so could tell us he needed a poo/wee and we'd sit him on the potty to do it all before he was able to talk - saved me changing a lot of stinky nappies! Longitudinally, our kids used baby sign and did/are doing well at school and have all been ahead with language skills (but that's not accounting for confounding variables).

It's curious to see infant developmental stages becoming more and more to be compared to AI/robot development.