Listen and read 20: Which is really the weaker sex? - Thấm Tâm Vy

Nội dung text: Listen and read 20: Which is really the weaker sex? - Thấm Tâm Vy

1. LISTEN AND READ 20 A long-standing hypothesis holds the sex chromosomes to blame. Evolution Male mammals are, in the jargon, heterogametic. They have X and Y chromosomes, whereas females have a pair of Xs. In birds, it is the Which is really the weaker sex? females which are heterogametic. In both groups, the sex- It depends on the way sex is determined in the first place determining chromosome is a stubby thing that is missing many of WOMEN LIVE longer than men. And more generally, female the genes on its counterpart. It therefore cannot cover for its partner’s mammals live longer than male ones. This might be put down to the genetic deficiencies by providing working copies of genes which are fact that males live more dangerous lives than females—competition mutated in that partner. (In humans, haemophilia, Duchenne for the affections of those females being an ingrained part of muscular dystrophy and colour-blindness are all caused this way.) malehood. Such competition leads either to dangerous fights, or to As a result, the heterogametic sex is less resilient and dies earlier. the growing of showyoffy but physiologically expensive and thus It is a plausible idea. But two sample points (mammals and birds) life-limiting accoutrements, or both. All of which would make do not prove it. So Zoe Xirocostas and her colleagues at the perfect sense were it not also true that male birds, which cede University of New South Wales, in Sydney, Australia have looked nothing to their mammalian counterparts in the fighting and further. As they describe in Biology Letters, they searched the showing-off departments, nevertheless manage, on average, to literature for animals where both the relative longevity of the sexes outlive their respective females. Male spruce grouse (pictured), for and the nature of any heterogameticity are known. Adding reptiles, example, live for 13 years; females for five. amphibians, sharks, bony fish, arachnids and insects to the list, they confirmed that the relationship between longevity and heterogameticity does indeed hold up in other groups of animals. But there is a twist. When males are heterogametic the sex difference in lifespan averages 20.9%. Despite extreme examples like the spruce grouse, however, when females are heterogametic the average difference is only 7.1%. These numbers suggest that fighting and showing off are involved in determining longevity differences, too. [From: The Economist US. 07.03.2020] Notes: - chromosomes : nhiễm sắc thể - heterogametic: dị-giao-tử - haemophilia: chứng loãng huyết (không đông máu) - Duchenne muscular dystrophy : chứng loạn-dưỡng cơ (giãn cớ) - arachnids : động vật thuộc họ nhện (spider) - spruce grouse: North American grouse that feeds on evergreen buds and needles. (gà gô Mỹ) Thẩm Tâm Vy, March 11, 2020 LISTEN AND READ 20 EVOLUTION