[填空题]
There are about 105 males born for every 100 females, but
this{{U}} (36) {{/U}}drops to near balance at the age of maturity, and
among 70-year olds there are twice as many women as men. But the great universal
of male{{U}} (37) {{/U}}is being changed. Now, boy babies{{U}} (38)
{{/U}}almost as well as girls do. Fifty years ago, the chance of a
baby(particularly a boy baby)surviving depended on its weight. A kilogram too
light or too heavy{{U}} (39) {{/U}}almost certain death. Today it makes
almost no{{U}} (40) {{/U}}. Since much of the variation is due to genes,
one more agent of evolution has gone.
There is another way to{{U}}
(41) {{/U}}evolutionary suicide: stay alive, but have fewer children.
Few people are as{{U}} (42) {{/U}}as in the past. Nowadays the number of
births, like the age of death, has become{{U}} (43) {{/U}}.Again,
{{U}} (44) {{/U}}.
For us, this means that evolution is
over; the biological Utopia