Why kids with larger heads walk late?

Lil' General took his first step unaided when he was two days short of turning 15 months old. He has been walking around the furniture since he was nine months old. But the delayed walking milestone - the biggest of them all was a huge concern for everyone around - his grandparents' in particular.

I wasn't too worried as his Paediatrician rightly pointed out when he was about six months telling me to anticipate a slight delay in all his milestones - crawling, sitting, walking etc. attributing it to his weight. He doesn't look healthy so to say... but it's there somewhere. National Geographic ran an interesting series yesterday on kids and how they reach every milestone of theirs. One particular section dealt at length about the relationship between kids with heavier (larger whatever you call) heads and the delayed walking milestone. The reasoning sounds logical and simple. The heavier the head, the difficult it is for the kid to find his center of gravity and stand up unaided. It takes so much longer as his shoulders broaden and can support his weight down enabling him to take the first step. LG has a huge head something that everyone notices first in him. So it's CG doing the trick :)

Here's a good site I found on growth and development of kids.