Recently the New York Times reported the following:
How Did Hands Evolve? The Answer Is Behind You. (1/2)
The evolutionary blueprint for hands was borrowed in part
from a much older genetic plan for our nether regions, a new study suggests.
By Carl Zimmer –
Origins
17 Sept. 2025
About 360 million years ago, our fishy ancestors moved from
water to land. Along the way, their fins turned into feet, with toes. And
hundreds of millions of years later, the front pair evolved into hands.
To understand this profound evolutionary transformation, scientists have spent decades studying the fossils of extinct fish that sported limb-like fins. They have also compared the embryos of modern-day fish and land vertebrates to understand how their fins and limbs develop.
“It’s much easier than if you had to build from scratch,” said Aurélie Hintermann, a postdoctoral researcher at the Stowers Institute for Medical Research, in Kansas City, Mo.
On Wednesday, Dr. Hintermann and her colleagues showed just how old some of those pieces were: The recipe for building hands was borrowed in part from the one for our nether regions.
Dr. Hintermann and her colleagues carried out their study by tracing the activity of genes in developing embryos. An embryo begins as a fertilized egg with a single set of genes; it then divides into new cells, each of which inherits those same genes. But along the way, the cells turn these genes on and off in different patterns, enabling them to become particular tissues and organs. The cells also send out molecules that trigger neighbors to change their own genetic melody.
Those signaling molecules switch genes on by grabbing DNA at a precise location, like a key turning in a lock. Many genes need several keys to open locks before they can become active.
Scientists have identified some of the locks that enable embryos of humans and other species to grow limbs. In 2011, Denis Duboule, a biologist at the University of Geneva, and his colleagues discovered a half-dozen molecular locks sitting side-by-side along a stretch of DNA called 5DOM. When 5DOM was snipped out of a mouse embryo’s DNA, the embryo grew legs but failed to grow feet.
Dr. Duboule and his colleagues wondered how this crucial set of locks evolved. Did it arise when our ancestors first came ashore and evolved limbs? Or did it exist earlier, in our finned ancestors?
To tackle that question, Christopher Bolt, then a graduate
student in Dr. Duboule’s lab, searched through the genome of the zebrafish. He
discovered that it, too, had 5DOM.
Zebrafish and mammals share an ancient common ancestor that lived more than 400 million years ago. The Geneva team’s discovery suggested that this primordial ancestor already had 5DOM. And if it was still intact in zebrafish, it must be doing something in their embryos. “It could not be there by chance,” Dr. Hintermann said.
(to be continued)
Translation
手是如何進化的？答案就在你的背後。 （1/2）
一項新研究表明，手的演化藍圖部分借鑒了我們更古老的生殖器官的基因排序藍圖。
大約3.6億年前，我們的魚類祖先從水中遷移到陸地。在此過程中，它們的鰭演化成有腳趾的腳了。數億年後，一對前鰭演變成手了。
為了理解這深刻的演化轉變，科學家花費數十年研究已滅絕魚類的化石，這些魚類都擁有類似肢體的鰭。他們也比較了現代魚類和陸生脊椎動物的胚胎，以了解它們的鰭和肢體是如何發展的。
如今，一種名為CRISPR的精準DNA編輯技術讓科學家能夠從分子層面重建這古老的演化變化。結果表明，手和腳並非由新的基因執行新的功能而產生的。相反，透過自然選擇，令構成遠古身體部位的古老基因排序被拼湊成新的組合。
密蘇裡州堪薩斯城斯托爾斯醫學研究所的博士後研究員Aurélie Hintermann說:「這比從零開始建造要容易得多」。
週三，Hintermann博士和她的同事們展示了其中一些基因篇排的古老程度：構建手部的基因譜部分借鑒自我們生殖器官的基因排序。
Hintermann博士和她的同事們透過追蹤發育中胚胎的基因活動來進行這項研究。胚胎最初是一個受精卵，擁有一套基因組；然後它分裂成新的細胞，每個細胞都繼承了相同的基因。但在此過程中，細胞會以不同的模式開啟和關閉這些基因，使它們能夠發育成特定的組織和器官。細胞也會釋放一些分子，觸發鄰近細胞改變自身的基因表現特徵或特性。
這些訊號分子透過在一特定位置抓住DNA來激活基因，就像鑰匙轉動鎖一樣。許多基因需要多把「鑰匙」才能打開「鎖」並被啟動。
科學家已經辨識出一些能夠使人類和其他物種的胚胎長出四肢的「鎖」。 2011年，日內瓦大學的生物學家Denis Duboule和他的同事在一段名為5DOM的DNA序列上發現了六個並排排列的分子「鎖」。當從小鼠胚胎的DNA中切除5DOM時，胚胎長出了腿，但沒有長出腳。
Duboule博士和他的同事想知道這組關鍵的「鎖」是如何演化而來的。它是在我們祖先首次登陸並進化出四肢時出現的嗎？還是更早存在於我們有鰭的祖先身上？
為了解答這個問題，當時在Duboule博士實驗室攻讀研究生的Christopher Bolt對斑馬魚的基因組進行了研究。他發現斑馬魚也擁有5DOM。
斑馬魚和哺乳動物擁有一個共同的古代祖先，生活在4億多年前。日內瓦團隊的發現表明，這個遠古祖先已經擁有5DOM基因。如果斑馬魚體內仍保留著5DOM基因，那麼它必然在斑馬魚胚胎發育過程中發揮某種作用。Hintermann博士說: 「它不可能是偶然存在的」。
（待續）
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