Katie Couric's Notebook: Bodies

You know what they say about people with big feet? They also have shrunken brains.

Let me explain.

Today The Wall Street Journal featured a graphic chart detailing how the human body has evolved over the past few thousand years.

While our feet have grown about four shoe sizes on average since 1900 the brain shrunk by 10 percent over 5000 years.

The gene for blue eyes is much more common today - although scientists say the advantage is unclear. Try telling that to Robert Redford.

Our skulls are rounder and thinner than they were ten thousand years ago, because, quote, we are less likely than our ancestors to be bashed with clubs.

At least we've got that going for us.

Some of the changes have made us stronger - but some have made us more prone to disease or obesity as we adjusted to new lifestyles over time.

So, if you don't like your ears or that spare tire you're carrying around - don't blame your mother. Blame evolution.

That's a page from my notebook.

I'm Katie Couric, CBS News.