A biological point of view on why we have eyebrows.

    Bottleneck Effect

    Well first let me go over why i find it strange that eyebrows are there. First of all the theory of evolution is that a beneficial mutation will obviously help the organism survive. These mutations may go unnoticed but will be there. The mutated organism breeds with other organisms, lets just use cows as an example. The mutation will take dominance in the genes so if the mutation provides an immunity to say a certain virus that cow will be immune. so back to the evolution theory, say there is an influx of the amount of virus infected cows. The immune ones will survive while most or all of the non immune ones will die. This will cause the cows that are immune to mate since they are the only mating options meaning all the offspring will have this immunization, this does lower the gene pool diversity but leaves all the cows immune to this virus. This is called the bottleneck effect. This bottleneck effect made the cows immune to the virus and helped them survive so the reason i find it strange eye brows are there is because, how did it help humans survive? What made the humans that didn't have eyebrows die?

    Catastrophism/Possible Bottleneck on Humans

    A possible reason for humans having eyebrows is that in a certain part of the earth there was a mutation that caused people to grow hair above their eyes. The catastrophism theory is that every once and a while an event will occur that wipes out most of the planets organisms, its what predicted happened to the dinosaurs and what may have possibly happened to the early human species. In this case the tribe or group that had eyebrows was the only one left surviving on the whole entire planet. This means that since their whole group had the dominant genes for eyebrows all the young are going to have eyebrows and the humans that evolved from them are going to have eyebrows aside from the ones that mutate again but in the modern day society we as humans are subject to artificial selection which is you choose who you make offspring with opposed to in the wild where animals mate with any other animal of the same species they can find. This artificial selection will be why less genetic variation will be happening to todays human species. There will have been less artificial selection millions of years ago in fact it would most likely be fully natural selection and that is a way that eyebrows may have been permanently built into the human genes. Well atleast my theory anyway.

    從生物學(xué)的角度解讀眉毛存在的必要性

    瓶頸效應(yīng)

    哦,先讓我想想為何奇怪眉毛長(zhǎng)在眼部上方。首先進(jìn)化論是一種有利的基因突變,明顯有助于有機(jī)體幸存。這些突變會(huì)不經(jīng)意間出現(xiàn)但的的確確發(fā)生在那。突變的有機(jī)體和其它有機(jī)體“相依為命”。我們就以奶牛為例吧!由于突變?cè)诨�因中占�?jù)中支配地位,因此,如果突變會(huì)對(duì)某中病毒產(chǎn)生一定的免疫力,那么奶牛就有免疫性�，F(xiàn)在我們回到進(jìn)化論的問題上。假設(shè)有大量病毒感染了牛群,有免疫力的奶牛就會(huì)幸存而無(wú)免疫力的大多數(shù)或所有奶牛將無(wú)法幸免。有免疫力的奶牛就因此配對(duì),因?yàn)檫@是它們的唯一選擇,這樣一來它們的幼仔也會(huì)有免疫作用,這減少了基因庫(kù)的多樣性但幸免的所有奶牛對(duì)病毒均具免疫性。這便是所謂的“瓶頸效應(yīng)”。它使得奶牛幸免于病毒而活下來,由此得出那原因在于:眉毛是如何使人類幸存下來的?又是什么使得那些沒眉毛的人無(wú)法幸存呢?

    災(zāi)變說/人類身上的可能瓶頸

    人類長(zhǎng)有眉毛,一個(gè)可能的原因就是地球某一區(qū)域發(fā)生過災(zāi)變,從而導(dǎo)致人眼上方長(zhǎng)有毛發(fā)。所謂災(zāi)變理論即每隔一定時(shí)期后會(huì)突發(fā)事故,徹底消滅大多數(shù)行星的有機(jī)體,就像人類預(yù)測(cè)的曾經(jīng)發(fā)生在恐龍和早期人類身上的災(zāi)害事故。為此,那些長(zhǎng)有眉毛的部落和人群是整個(gè)星球的唯一幸存者。自那些人具備了支配性的眉毛基因后,他們的后代長(zhǎng)有眉毛;進(jìn)化而來的人類長(zhǎng)有眉毛;那些再次基因突變的人群也長(zhǎng)有眉毛。但在現(xiàn)代社會(huì),作為人類的我們受到“人為淘汰”的影響,可以選擇誰(shuí)是自己的子孫,而不同于野生動(dòng)物,他們只能和自己找到的同一物種進(jìn)行交配。這種所謂的“人為淘汰”將是當(dāng)今人類物種為何發(fā)生較小基因突變的最好詮釋。事實(shí)上在數(shù)百萬(wàn)年前很少有這種“人為淘汰”而絕大多數(shù)是“物競(jìng)天擇”,這也就是為什么眉毛永遠(yuǎn)是人類基因的一部分。好了,無(wú)論如何,這至少是我的理論。