揭開我們祖先直立行走的基因（1/2）

 Recently the New York Times picked up the following:

Source: The NYT

Uncovering the Genes That Let Our Ancestors Walk Upright (1/2)

A new study reveals some of the crucial molecular steps on the path to bipedalism.

Origins -By Carl Zimmer who covers news about science for The Times and writes the Origins column.

Aug. 27, 2025

Charles Darwin unveiled his theory of evolution in 1859, in “On the Origin of Species.” But it took him another 12 years to work up the courage to declare that humans evolved, too.

In “The Descent of Man,” published in 1871, Darwin argued that humans arose from apes. And one of the most profound changes they underwent was turning into upright walkers.

“Man alone has become a biped,” Darwin wrote. Bipedalism, he declared, was one of humanity’s “most conspicuous characters.”

Scientists have now discovered some of the crucial molecular steps that led to that conspicuous character millions of years ago. A study published in the journal Nature on Wednesday suggests that our early ancestors became bipeds, as old genes started doing new things. Some genes became active in novel places in the human embryo, while others turned on and off at different times.

Scientists have long recognized that a key feature for walking upright is a bone called the ilium. It’s the biggest bone in the pelvis; when you put your hand on your hip, that’s the ilium you feel.

The left and right ilium are both fused to the base of the spine. Each ilium sweeps around the waist to the front of the belly, creating a bowllike shape. Many of the leg muscles we use in walking are anchored to the ilium. The bone also supports the pelvic floor, a network of muscles that acts like a basket for our inner organs when we stand up.

As vital as the ilium is to everyday life, the bone can also be a source of suffering. The ilium can flare up with arthritis, grow brittle in old age, especially in women, and fracture from a fall. Genetic disorders can deform it, making walking difficult. The ilium also forms much of the birth canal — where babies can sometimes get stuck, endangering the mother’s life.

And yet, as important as the ilium is to us, its development has long been a mystery. “It’s remarkable to me,” said Terence Capellini, a developmental geneticist at Harvard. “The ilium is essential to how we walk and how we give birth, and yet very little is known about it.”

Dr. Capellini and his colleagues embarked on an intensive study of the bone. As part of the research, Gayani Senevirathne, a postdoctoral researcher at Harvard, examined human fetal tissue from a University of Washington repository. Dr. Senevirathne created three-dimensional models of the human ilium as it developed in embryos. She also analyzed the different types of cells that combine to form the bone, as well as the genes that switch on and off inside those cells.

She then did similar experiments on mice, dissecting their embryos and analyzing the cells in the developing ilium. Comparing the two species, she gathered some clues about how our own ilium evolved.

But there were limits to what mice could tell her, since they are only distantly related to humans. To get a better sense of what sort of ilium early humans inherited, Dr. Senevirathne needed to look at primates.

She reached out to museums across the United States and Europe to see if they had any primate specimens. She tracked down embryos of chimpanzees, gibbons and other species preserved in jars, and arranged for museum curators to scan them for her.

One day on her quest for material, she left Boston before dawn and drove to the American Museum of Natural History in New York. There, she loaded the car with crates of 100-year-old glass slides, each preserving a slice of a lemur embryo. Then she drove right back home.

“I was worried that we’d get pulled over by the police,” Dr. Senevirathne said. “But it was definitely worth it. We actually needed that material to complete our story.”

All told, the researchers studied 18 different species of primates. “The fact that they assembled so many embryonic samples was really impressive,” said Camille Berthelot, an evolutionary geneticist at the Pasteur Institute in Paris who was not involved in the study.

(to be continued)

揭開我們祖先直立行走的基因（1/2）

一項新研究揭示了雙足行走過程中一些關鍵的分子步驟。

達爾文於1859年在《物種起源》中提出了他的進化論。但他又花了12年才鼓起勇氣宣佈人類也進化。

在1871年出版的《人類的由來》中，達爾文認為人類起源於猿類。而他們經歷的最深刻的變化之一就是變成了直立行走的動物。

達爾文寫道: 「只有人類變成了兩足動物」。他宣稱，雙足行走是人類「最顯著的特徵」之一。

科學家們如今發現了數百萬年前導致這一顯著特徵的一些關鍵分子步驟。週三發表在《自然》雜誌上的一項研究表明，隨著舊基因開始產生新的功能, 我們的早期祖先變成了兩足動物。有些基因在人類胚胎的新位置变得活躍，而有些基因則在不同的時間開啟和關閉。

科學家早已認識到，直立行走的一個關鍵特徵是髂骨。它是骨盆中最大的骨頭；當你把手放在臀部時，你感覺到的就是髂骨。

左右髂骨都與脊椎底部融合。每塊髂骨繞過腰部，延伸至腹部前方，形成碗狀。我們行走時使用的許多腿部肌肉都固定在髂骨上。髂骨也支撐著骨盆底肌肉網絡，當我們站立時，骨盆底肌肉網絡就像一個籃子，容納我們體內的器官。

髂骨對日常生活至關重要，但它也可能帶來疼痛。髂骨會因關節炎發作，在老年時（尤其是女性）會變得脆弱，跌倒後會導致骨折。遺傳性疾病會導致髂骨變形，使行走困難。髂骨也構成了產道的大部分 - 嬰兒有時會卡在那裡，危及母親的生命。

然而，儘管髂骨對我們至關重要，但它的發育長期以來一直是個謎。哈佛大學發育遺傳學家Terence Capellini 說: 「它對我來說意義非凡」; 「髂骨對於我們行走和分娩至關重要，但人們對它的了解卻少之又少」。

Capellini 博士和他的同事們對髂骨進行了深入研究。作為研究的一部分，哈佛大學博士後研究員Gayani Senevirathne 檢查了華盛頓大學儲存庫中的人類胎兒組織。Senevirathne 博士創建了人類髂骨在胚胎中發育的三維模型。她也分析了構成骨骼的不同類型的細胞，以及這些細胞內的開啟和關閉的基因。

隨後，她對小鼠進行了類似的實驗，解剖了它們的胚胎，並分析了發育中髂骨的細胞。透過比較這兩個物種，她收集了一些關於我們自身髂骨演化的線索。

但由於小鼠與人類的親緣關係較遠，因此它們能提供的線索有限。為了更了解早期人類遺傳了哪一種髂骨，Senevirathne 博士需要看看靈長類動物。

她聯繫了美國和歐洲各地的博物館，看看它們是否有靈長類動物標本。她找到了保存在罐子裡的黑猩猩、長臂猿和其他物種的胚胎，並安排博物館館長為她掃描這些胚胎。

有一天，為了尋找資料，她在黎明前離開波士頓，開車前往紐約的美國自然史博物館。在那裡，她把一箱箱有百年歷史的玻璃幻燈片裝上車，每箱載玻片都保存著一片狐猴胚胎。然後她直接開車回家。

Senevirathne博士說: 「我擔心我們會被警察攔下來」; 「但這絕對值得。我們確實需要這些材料來完成我們的故事」。

總而言之, 研究人員研究了18種不同的靈長類動物。沒有參與這項研究的巴黎巴斯德研究所的進化遺傳學家 Camille Berthelot 說道: 「他們收集瞭如此多的胚胎樣本，真是令人印象深刻」。

（待續）