Are men faster than women, or did they just get a head start?

I am working on the Gender Stratification lesson plan for an Intro to Sociology class I am teaching, and I came across the following piece of gender history:

Not until 1984 in Los Angeles would the women's marathon become a sanctioned Olympic event. Joan Benoit Samuelson, the winner, had attended high school in Maine, where women's track teams were not granted varsity status during her freshman and sophomore years. She won the 1975 state championship in the mile -- the longest distance a woman was allowed to run -- but because she insisted on practicing with the boys to improve her times, she was denied the school's most valuable athlete award. "That's when I said to myself, 'I'll show that coach -- I'm going to win an Olympic medal some day,' " Samuelson says. Nine years later she did.
NY Times (1996)

In the era of Title IX it is difficult to remember that less than a generation ago, women were not grated equal access to sports (not to mention certain educational or occupational opportunities). Improvements in gender equity since the 1960s have been rapid, but the effects of gender discrimination linger.

One of the most common excuses for excluding women from certain endeavors has always been that they are not as ______ as men (insert "strong," "fast," "smart," "tough," or any number of other adjectives here).

But are women really weaker or slower than men?

Or did they just get a late start?

Today's marathon world record, still held by Paula Radcliffe from the 2003 London Marathon, represents a pace that is equivalent to the fastest man on earth in the early 1960s. And while men's marathon times have remained (from a statistical perspective) roughly stable over the last century, dropping from 2:55 in 1909 to 2:03:59 in 2006, women's times have seen rapid improvement.

Comparatively speaking, men dropped about 50 minutes off of their record times (for an improvement of 29 percent over 100 years). During the same period women's record times dropped by more than three hours, for an improvement of 60 percent over the same 100 years.

Today the differential in men's and women's paces can be measured in seconds per mile, not minutes.

In 1980 only 10 percent of marathon runners were female. In 2009 the proportion reached 41 percent (data from Running USA). The share of women running in shorter races has risen even faster. In the half-marathon distance, women became the majority of runners in 2005.

And, perhaps most interestingly, women who enter ultra-marathons (any distance longer than 26.2 miles) have a substantially higher likelihood of completing the race than male entrants do.

So it is entirely possible that women can be just as fast as men, but got a late start in this game. Granted, there are runners who make a strong argument to the contrary by suggesting that over the last couple of decades the disparity in paces between men and women has remained roughly constant both in the marathon and in other distances.

This is one case where only time will tell.

Chart data source:
http://www.marathonguide.com/history/records/
data compiled by author