随身英语 Hair and evolution 毛发和进化论
Play audio file 为什么进化后的人类毛发稀疏？而和我们人类最近似的动物王国里的亲戚则仍全身匹着毛发？在物种进化过程中，毛发稀疏的人类是如何确保自己能成功生存下来？本期《随身英语》谈论毛发和人类进化的关系。
课文内容 词汇: Evolution 进化
Compared to other large mammals on Earth, we humans have relatively little hair. This obvious fact is not so strange until we look at our closest living relatives in the animal kingdom – chimpanzees and other great apes. Why, might we ask, have we evolved to be almost hairless when all other primates are still covered in fur? In fact, bizarre as it may seem, our lack of hair has been the key to our evolutionary success as a species.
The question why our earliest ancestors lost their hair when fur would have been beneficial to them – for keeping warm on cold nights, for example – was pondered by Charles Darwin, the famous evolutionist: "No one supposes that the nakedness of the skin is any direct advantage to man." He concluded that the reason hominins lost their hair was sexual selection. In other words, we prefer our partners to have little hair. But what caused our ancestors to start losing their hair before this preference set in?
The most likely hypothesis to explain the loss of hair is that it became necessary when early hominids moved to a more open savannah habitat around 2 to 3 million years ago, when they started to hunt big game.Hunting in open savannah meant being exposed to the strong heat of the sun for several hours in the day and being in danger of overheating. Being covered in hair prevented our ancestors from losing heat fast enough. So, as Peter Wheeler, of Liverpool John Moores University in the UK, explained, losing hair allowed them to develop the ability to sweat and therefore to cool down. Early humans could, as a consequence, be out at midday hunting and foraging. "It would be [an] enormous advantage to be able to spend the entire midday foraging, finding mates or fighting enemies", Tamás Dávid-Barrett of Oxford University says. "Sweating allows that, and for sweat to be efficient you need to be mostly hairless". The meat from hunting animals gave early humans the energy to fuel their growing brain.
Humans are the sweatiest primates on Earth. They have up to 5 million sweat glands,which produce about 12 litres of sweat per day. It's this propensity to sweat that accounts for our hairlessness and has allowed us to thrive. It might help to remember this next time you're surrounded by sweaty hairless torsos in the gym!
词汇表 primates 灵长目动物
bizarre 奇怪的，离奇的
species （动植物的）物种
to ponder 思索，考虑
evolutionist 进化论者
nakedness 裸露
hominins 古人类
sexual selection 雌雄淘汰
ancestor 祖先
hypothesis 假说，假设
hominids 原人
savannah 稀树草原
to hunt 打猎
game 野禽
early human 早期人类
foraging 觅食，搜寻食物
find a mate 寻找配偶
gland 腺
propensity 习性，倾向
to thrive 长得健壮
torso （人体的）躯干
测验与练习 1. 阅读课文并回答问题。
1. True or false? All primates are covered in fur.
2. Who was Charles Darwin?
3. Why was moving to the savannah a problem for our early ancestors?
4. What is the advantage of having little hair in a hot climate?
5. What link does the author make between hunting meat and human success?
2. 请你在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处 。
1. I discovered the other day that I have a __________ relative living in Greenland. She's actually my first cousin.
direct close good near
2. Darwin explained his famous __________ theory of natural selection in 1859 in his book 'On the Origin of Species'.
revolutionary evolutionary evolution extraordinary
3. If babies wear too many clothes in hot weather, they are at __________ of overheating.
risk danger likely possibility
4. Daniel __________ hard work. He's happiest when he's got lots of problems to solve at the office.
thrives at thrives on thrives with thrive on
5. Our human ancestors lost hair because this allowed them to sweat with the greatest __________.
effort deficiency efficiency sufficiency
答案 1. 阅读课文并回答问题。
1. True or false? All primates are covered in fur.
False. Humans only have a little hair on their bodies compared to other primates.
2. Who was Charles Darwin?
He was a famous evolutionist.
3. Why was moving to the savannah a problem for our early ancestors?
Because it meant that they were exposed to long hours of strong sun and they were in danger of overheating.
4. What is the advantage of having little hair in a hot climate?
It means that you can sweat efficiently.
5. What link does the author make between hunting meat and human success?
The author explains that eating meat provided energy that helped the brain to develop.
2. 请你在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处 。
1. I discovered the other day that I have a close relative living in Greenland. She's actually my first cousin.
2. Darwin explained his famous evolutionary theory of natural selection in 1859 in his book 'On the Origin of Species'.
3. If babies wear too many clothes in hot weather, they are at risk of overheating.
4. Daniel thrives on hard work.
5. Our human ancestors lost hair because this allowed them to sweat with the greatest efficiency.