填空题

There are about 105 males born for every 100 females, but this (36) 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 (37) is being changed. Now, boy babies (38) 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 (39) almost certain death. Today it makes almost no (40) . Since much of the variation is due to genes, one more agent of evolution has gone. There is another way to (41) evolutionary suicide: stay alive, but have fewer children. Few people are as (42) as in the past. Nowadays the number of births, like the age of death, has become (43) . Again, (44) . For us, this means that evolution is over; the biological Utopia has arrived. Strangely, it has involved little physical change. No other species fills so many places in nature. (45) We did not evolve, because machines and society did it for us. Darwin had a phrase to describe those ignorant of evolution: they "look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension." No doubt we will remember a 20th century way of life beyond comprehension for its ugliness. (46) .