Human Skeleton Illustration

人为什么要直立行走? 哈佛生物学家揭秘

人体骨骼图

与黑猩猩和大猩猩相比,我们的骨盆刀片的更短和更宽的重新定位使人类能够更轻松地行走或平衡。

一项新的研究展示了骨盆是如何为直立行走而进化的。

如果进化生物学家特伦斯·D·卡佩里尼(Terence D. Capellini)对将我们定义为人类的身体部位进行排名,骨盆将位于顶部。

毕竟,由于它的设计,人类可以用两条腿直立行走(与我们的灵长类表亲不同),母亲可以生下头很大的孩子(因此大脑很大)。 骨盆在解剖学上是众所周知的,但是当谈到这个非常重要的结构在整个发育过程中如何以及何时形成时,我们的理解就开始动摇了。

由于 Capellini 团队最近的研究,这种情况正在发生变化。 该研究发表在期刊上 科学进步,演示在怀孕期间骨盆何时形成并确定驱动该过程的基因和基因序列。 有朝一日,这项研究可能会深入了解双足行走的遗传起源,并为开发髋关节疾病的治疗方法或预测因子铺平道路,如髋关节发育不良和髋关节骨关节炎。

“这篇论文真正关注的是所有人类的共同点,即骨盆的这些变化使我们能够用两条腿走路并让我们生下一个大胎头,”该系新任终身教授 Capellini 说哈佛大学人类进化生物学博士和该研究的高级作者。

研究表明,人类行走和分娩所必需的许多特征在怀孕 6 到 8 周左右形成。 这包括人类独有的关键骨盆特征,例如其弯曲和盆状的形状。 这种形成发生在骨骼仍然是软骨的时候,因此它们可以很容易地弯曲、旋转、扩张和生长。

研究人员还发现,当身体中的其他软骨开始转化为骨骼时,发育中的骨盆区域会在较长时间内保持软骨状态,使其能够正常成熟。

“似乎发生了停滞,这种停滞使软骨仍然生长,这很有趣,也很令人惊讶,”卡佩里尼说。 “我称之为保护区。”

研究人员使用

核糖核酸
核糖核酸 (RNA) 是一种类似于 DNA 的聚合分子,在基因的编码、解码、调节和表达中的各种生物学作用中是必不可少的。 两者都是核酸,但与 DNA 不同,RNA 是单链的。 RNA 链的骨架由交替的糖(核糖)和磷酸基团组成。 与每种糖相连的是四种碱基之一——腺嘌呤 (A)、尿嘧啶 (U)、胞嘧啶 (C) 或鸟嘌呤 (G)。 细胞中存在不同类型的 RNA:信使 RNA (mRNA)、核糖体 RNA (rRNA) 和转移 RNA (tRNA)。

“数据-gt-翻译-属性=”[{” attribute=””>RNA sequencing to determine which genes in the area are actively triggering pelvic formation and slowing ossification, which usually converts softer cartilage to hard bone. They discovered hundreds of genes that are turned either on or off throughout the 6- to 8-week period to form the ilium in the pelvis, which is the largest and uppermost bone of the hip with blade-like structures that curve and rotate into a basin to support walking on two legs.

Compared to chimpanzees and gorillas, the shorter and wider reorientation of our pelvic blades makes it so humans don’t have to shift the mass of our weight forward and use our knuckles to walk or balance more comfortably. It also helps increase the size of the birth canal. Apes on the other hand have much narrower birth canals and more elongated ilium bones.

The researchers started the study by comparing these differences in hundreds of skeletal samples of humans, chimpanzees, and gorillas. The comparisons demonstrated the striking effects that natural selection has had on the human pelvis, the ilium in particular.

To see when the ilium and pelvic elements forming the birth canal began to take shape, the researchers examined 4- to 12-week-old embryos under a microscope with the consent of people who had legally terminated their pregnancies. The researchers then compared samples from the developing human pelvis’ with mouse models to identify the on and off switches triggering the formation.

The work was led by Mariel Young, a former graduate researcher in Capellini’s lab who graduated in 2021 with her Ph.D. The study was a collaboration between Capellini’s lab and 11 other labs in the U.S. and around the world. Ultimately, the group wants to see what these changes mean for common hip diseases.

“Walking on two legs affected our pelvic shape, which affects our disease risk later,” Capellini said. “We want to reveal that mechanism. Why does selection on the pelvis affect our later disease risk of the hip, like osteoarthritis or dysplasia? Making those connections at the molecular level will be critical.”

Reference: “The developmental impacts of natural selection on human pelvic morphology” by Mariel Young, Daniel Richard, Mark Grabowski, Benjamin M. Auerbach, Bernadette S. de Bakker, Jaco Hagoort, Pushpanathan Muthuirulan, Vismaya Kharkar, Helen K. Kurki, Lia Betti, Lyena Birkenstock, Kristi L. Lewton and Terence D. Capellini, 17 August 2022, Science Advances.
DOI: 10.1126/sciadv.abq4884

The study was funded by Harvard University, the National Science Foundation, and the Milton Fund, 


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