???????1835 年，在他提出進(jìn)化論之前，查爾斯·達(dá)爾文從孤立的加拉帕戈斯群島收集了 13 種以前不為人知的雀類的標(biāo)本。加拉帕戈斯雀與生活在南美洲大陸的一種雀非常相似，但每種加拉帕戈斯雀都有一個(gè)獨(dú)特的形狀不同的喙。群島[加拉帕戈斯群島]，為了不同的目的，已經(jīng)采取和修改了一個(gè)物種?！癟h這就是達(dá)爾文自然選擇進(jìn)化論的精髓：具有特定喙形的鳥類得以幸存和繁殖，因?yàn)樗鼈兊泥故顾鼈兡軌蚝芎玫剡m應(yīng)使用特定的食物來(lái)源。就這樣，一個(gè)從大陸來(lái)到加拉帕戈斯的原始物種最終進(jìn)化成了13個(gè)新物種。

???????13 種雀科物種的喙與其食物來(lái)源之間的對(duì)應(yīng)關(guān)系立即向達(dá)爾文表明進(jìn)化塑造了它們。如果他關(guān)于祖先雀鳥的喙是由進(jìn)化形成的說(shuō)法是正確的，那么應(yīng)該可以看到不同種類的雀鳥發(fā)揮它們的進(jìn)化作用，每一種都使用它們的喙來(lái)獲得它們特定的食物特性。這四個(gè)例如，那些用喙壓碎種子的物種應(yīng)該以不同的種子為食，那些喙較粗的物種專攻難以壓碎的種子。

???????許多生物學(xué)家在達(dá)爾文之后訪問(wèn)了加拉帕戈斯群島，但直到 100 年后，當(dāng)偉大的博物學(xué)家大衛(wèi)·萊克（avid Lack）終于在 1938 年開始著手對(duì)這些鳥類進(jìn)行了整整五個(gè)月的密切觀察時(shí)，他的假設(shè)才進(jìn)行了這一關(guān)鍵測(cè)試，他的觀察似乎反對(duì)達(dá)爾文的提議。萊克經(jīng)常觀察到許多不同種類的雀類以同一種子為食。我們現(xiàn)在知道，在雨季研究鳥類是拉克的不幸，當(dāng)時(shí)食物充足。在這樣的沖水時(shí)期，雀的喙并不重要。小種子是如此豐富，以至于所有物種的鳥類都能獲得足夠的食物。

???????成功驗(yàn)證達(dá)爾文關(guān)于加拉帕戈斯雀的喙適應(yīng)不同食物來(lái)源的建議的關(guān)鍵：證明是耐心。從 1973 年開始，普林斯頓大學(xué)的 Peter 和 Rosemary Grant 以及他們的幾代學(xué)生在加拉帕戈斯群島中心的一個(gè)名為 aphne Major 的小島上研究了中型地雀 Geospiza fortis。這些雀類優(yōu)先以潮濕年份植物大量生產(chǎn)的小而嫩的種子為食。只有當(dāng)小種子在長(zhǎng)時(shí)間干燥的天氣中枯竭并且植物產(chǎn)生很少的種子時(shí)，鳥類才會(huì)求助于更大、更干燥的種子，這些種子更難壓碎。

???????The Grants quantified beak shape among the medium ground finches of aphne Major by carefully measuring beak depth(width of beak, from top to bottom,at its base) on individual birds. Measuring many birds every year, they were able to assemble a detailed portrait of evolution in action.' The Grants found that beak depth changed from one year to the next in a predictable fashion. uring droughts, plants: produced few seeds and all available small seeds were quickly eaten, leaving large seeds as the remaining source of food. s a result, birds with large beaks survived better, because they were better able to break open these large seeds. onsequently, the average beak depth of birds in the population increased the next year,only to decrease again when wet seasons returned.

???????ould these changes in beak dimension reflect the action of natural selection? n alternative possibility might be that the changes in beak depth do not reflect changes in gene frequencies, but rather are simply a response to diet- -perhaps during lean times the birds become malnourished and then grow stouter beaks, for example. If this were the case, it would not be genetics but environment alone that influences beak size. To rule out this possibility, the Grants measured the relation of parent bill size to offspring beak size, examining many broods over several years. The depth of the beak was passed down faithfully from one generation to the next, regardless of environmental conditions, suggesting that the differences in beak size indeed reflected genetic differences.

1. 1835 年，在他提出進(jìn)化論之前，查爾斯·達(dá)爾文從孤立的加拉帕戈斯群島收集了 13 種以前不為人知的雀類的標(biāo)本。加拉帕戈斯雀與生活在南美洲大陸的一種雀非常相似，但每種加拉帕戈斯雀都有一個(gè)獨(dú)特的形狀不同的喙。群島[加拉帕戈斯群島]，為了不同的目的，已經(jīng)采取和修改了一個(gè)物種。“Th這就是達(dá)爾文自然選擇進(jìn)化論的精髓：具有特定喙形的鳥類得以幸存和繁殖，因?yàn)樗鼈兊泥故顾鼈兡軌蚝芎玫剡m應(yīng)使用特定的食物來(lái)源。就這樣，一個(gè)從大陸來(lái)到加拉帕戈斯的原始物種最終進(jìn)化成了13個(gè)新物種。?

2.The correspondence between the beaks of the 13 finch species and their food source immediately suggested to arwin that evolution had shaped them. If his suggestion that the beak of an ancestral finch had been shaped by evolution is correct,then it ought to be possible to see the different species of finches acting out their evolutionary roles, each using their beaks to acquire their particular food specialty.The four species that crush seeds within their beaks, for example, should feed on different seeds, those with stouter beaks specializing in harder-to- crush seeds.