[00:07.51]Being a man has always been dangerous.
[00:10.94]There are about 105 males born for every 100 females,
[00:17.09]but this ratio drops to near balance at the age of maturity,
[00:21.84]and among 70-year-olds there are twice
[00:24.16]as many women as men.
[00:27.18]But the great universal of male mortality is being changed.
[00:32.34]Now, boy babies survive almost as well as girls do.
[00:37.40]This means that, for the first time,
[00:39.91]there will be an excess of boys in those crucial years
[00:43.24]when they are searching for a mate.
[00:46.06]More important, another chance for natural selection
[00:49.58]has been removed.
[00:51.60]Fifty years ago, the chance of a baby
[00:54.93](particularly a boy baby) surviving depended on its weight.
[01:00.98]A kilogram too light or too heavy meant
[01:04.00]almost certain death.
[01:06.01]Today it makes almost no difference.
[01:09.04]Since much of the variation is due to genes,
[01:12.26]one more agent of evolution has gone.
[01:16.49]There is another way to commit evolutionary suicide:
[01:20.36]stay alive, but have fewer children.
[01:24.28]Few people are as fertile as in the past.
[01:27.30]Except in some religious communities,
[01:30.22]very few women have 15 children.
[01:33.55]Nowadays the number of births,
[01:35.87]like the age of death, has become average.
[01:39.80]Most of us have roughly the same number of offspring.
[01:43.62]Again, differences between people
[01:46.45]and the opportunity for natural selection to
[01:49.17]take advantage of it have diminished.
[01:51.99]India shows what is happening.
[01:54.97]The country offers wealth for a few in the great cities
[01:59.02]and poverty for the remaining tribal peoples.
[02:02.35]The grand mediocrity of today
[02:04.77]--everyone being the same in survival
[02:07.20]and number of offspring
[02:09.00]--means that natural selection has lost 80% of
[02:12.03]its power in upper-middle-class India
[02:15.16]compared to the tribes.
[02:17.78]For us, this means that evolution is over;
[02:21.86]the biological Utopia has arrived.
[02:24.99]Strangely,it has involved little physical change.
[02:29.52]No other species fills so many places in nature.
[02:33.45]But in the past 100,000 years
[02:36.38]--even the past 100 years
[02:38.70]--our lives have been transformed
[02:40.82]but our bodies have not.
[02:42.92]We did not evolve, because machines
[02:45.36]and society did it for us.
[02:48.38]Darwin had a phrase to describe those ignorant of evolution:
[02:53.01]they "look at an organic being as a savage looks at a ship,
[02:57.56]as at something wholly beyond his comprehension."
[03:00.90]No doubt we will remember a 20th century way of life
[03:04.78]beyond comprehension for its ugliness.
[03:07.71]But however amazed our descendants may be
[03:10.13]at how far from Utopia we were,
[03:12.75]they will look just like us.内容来自 听力课堂网：http://www.tingclass.net/show-8686-250979-1.html