脊椎的起源
Run, climb, breathe deep.
奔跑，攀爬，再来个深呼吸。
You might not connect those abilities to your backbone.
你可能不会感觉这些能力跟脊椎有关。
In fact, mammals owe many of their capabilities to the complex structure of their spine, which has five distinct regions, each free to adopt specialized functions.
事实上，哺乳动物的很多能力都要归功于其脊椎的复杂结构，它有五个不同的区段，每一段都拥有特定的功能。
In today's issue , Harvard University vertebrate paleontologist Stephanie Pierce and postdoc Katrina Jones report an investigation of fossils from the dawn of mammals that shows how evolution built our versatile spine.
在本期推文中，哈佛大学的脊椎动物古生物学家斯蒂芬.皮尔斯和博士后卡崔娜.琼斯介绍了一项对哺乳动物早期化石的研究，也许可以展示进化是如何造就了我们的万能的脊椎的。
"This is an important analysis," says Richard Blob, a biomechanist at Clemson University in South Carolina.
“这是一项很重要的分析研究，”理查德.布罗布说道，他是南卡罗莱纳州克莱姆森大学的一名生物力学家。
"It's tackling a fundamental problem: the origins of animal construction."
“它试图解决的是一个很基本的问题：动物结构的起源。”
And it shows how mammals ended up with a backbone that "can evolve in pieces and respond to different selective pressures at different places along the column," says Emily Buchholtz, a vertebrate paleontologist at Wellesley College in Massachusetts.
它展示了哺乳动物是如何进化成“可以分块进化，并在不同的地方对不同的选择压力做出反应”的骨架的，”艾米丽.布赫霍尔茨说道，她是马萨诸塞州威尔斯林学院的一名脊椎动物古生物学家。
Biologists have long recognized distinct regions in the mammalian spine based on their vertebrae.
生物学家早就根据哺乳动物的脊椎骨识别出了脊柱的不同的区域。
For example, small cervical vertebrae make up the neck, thoracic vertebrae bear the ribs and support the chest, and the ribless, hefty lumbar vertebrae bring up the rear.
例如，脊柱的颈部小段组成了脖子，胸段长出了肋骨撑起了胸腔，而没有肋骨的强力的腰椎段位于最后。
In contrast, reptiles and amphibians have very uniform backbones.
相比之下，爬行类和两栖类则拥有非常独特的脊椎。
"All their vertebrae are essentially doing the same thing," Pierce says.
“它们的脊椎从本质上起到的是同样的作用，”皮尔斯说道。
She and others assumed a regionalized spine was unique to mammals.
她和其他科学家们认为分段化的脊椎是哺乳动物特有的。
But in 2015, a sophisticated statistical analysis of a snake spine and a look at the genetic programs controlling its development indicated this backbone, too, has very subtly defined regions.
不过2015年时，一项对蛇的脊椎的精细的统计分析，以及对控制其进化的遗传编码研究表明，蛇的脊柱，也拥有微妙的区段划分。
"The work showed that regions could be distinct even if they weren't as different as in mammals," says Christian Kammerer, a paleontologist at the North Carolina Museum of Natural Sciences in Raleigh.
“这项研究表明即便跟哺乳动物不一样，这些区段也是不同的，”克里斯蒂安.卡莫勒说道，他是罗利市的北卡罗莱纳州自然科学博物馆的一名古生物学家。
The finding suggested a regionalized vertebral column evolved early in land animal history, even before the divergence of mammals and reptiles.
这项研究还表示分段化的脊柱在陆生哺乳动物早期历史上就演化出来了，甚至比演化出哺乳动物和爬行类分枝的时间更早。
To probe its origins, Pierce, Jones, and their colleagues scoured museums for fossils with complete backbones.
为了探究其起源，皮尔斯，琼斯和他们的同事们搜寻了四处的博物馆寻找带有完整脊柱的化石。
Ultimately, they analyzed spines from 16 synapsids, creatures that lived 200 million to 300 million years ago and include distant and immediate predecessors to mammals.
最后，他们分析了来自16种合弓纲的脊椎，这些生物生活在两三亿年前，研究还包括了哺乳动物的远的和近的先祖。
They used computerized tomography scanning to get high-resolution images and worked with paleontologist David Polly from Indiana University in Bloomington to precisely measure the shapes of the vertebrae and assess regionalization within each animal.
他们利用计算机拓扑扫描来获得高分辨率的图像，还跟布鲁明顿市的印第安纳大学的大卫.波利合作来准确测量脊椎的形状并对每种动物的分段进行评估。
The analysis uncovered a stepwise addition of regions.
研究揭示了分区的逐步增加。
More distant ancestors of mammals, such as Dimetrodon, a large reptilelike synapsid with a giant sail on its back, had three regions, designated cervical, anterior dorsal, and posterior dorsal.
哺乳动物更远的祖先，例如异齿龙，它是一种大型的爬行动物类的合弓纲动物，背上有巨大的背帆，它的脊柱有三段，特定的颈段，前背段和后背段。
The therapsids, creatures that just preceded mammals, had a fourth region, the pectoral.
而兽孔类，这种生物刚好在哺乳动物之前，拥有第四个区段，胸段。
A fifth region, the lumbar, appeared after early, egg-laying mammals arose and is found today in placental and marsupial mammals.
第五个区段，尾段，是在早期的产卵的哺乳动物后出现的，在如今的胎盘和有袋类哺乳动物中都有出现。
The work also pointed to factors driving the emergence of these distinct regions.
该研究还指出了催生这些独特区段产生的因素。
The pectoral region, for example, appeared in the therapsids as they evolved longer forelimbs, positioned under the body rather than splayed to the sides.
胸段，比方说，是随着它们进化出更长的前肢在兽孔类中出现的，前肢位于身体的下方而不是向两侧伸展。
(Think of a dog's legs compared with a lizard's.)
（可以想想狗和蜥蜴的腿的对比。）
The limb changes would have required changes in the shoulder girdle and the vertebrae supporting it, resulting in a distinct region of the spine just behind the neck.
肢体的变化就要求肩胛带和支持它的脊柱的变化，最后导致了脊柱紧随脖子的独特区段的诞生。
The same set of changes also freed some shoulder muscles to evolve into a muscular diaphragm, which improved breathing and enabled mammals to have a higher metabolic rate, Buchholtz says.
这同样的一系列变化还解放了肩部的一些肌肉，它们进化成了肌肉隔膜，它可以改善呼吸，使得哺乳动物能够拥有更高的新陈代谢速率，布赫霍尔茨说道。
Over time, further decoupling led to the modular spine seen in mammals today, in which individual vertebrae can change without jeopardizing the function of the whole spine.
随着时间的推移，进一步的分离导致了今天哺乳动物的模块化脊柱，在这种情况下，单个椎骨可以在不损害整个脊柱功能的情况下发生变化。
As a result, different regions can "take on new forms and functions, so they can adapt to different environments," Pierce says.
因此，不同的区块“可以有新的形式和功能，这样它们就能适应不同的环境，”皮尔斯说道。
Perhaps the most variable part of the spine has been the last to emerge: the lumbar region, which interacts with the pelvis and hind limbs.
脊椎最易变化的部分可能是最后出现的部分:与骨盆和后肢相互作用的腰椎区域。
The cat family illustrates the benefits of the region's evolutionary freedom.
猫科动物家族展示了该区段独立进化的好处。
All cats look, well, catlike, but lions tend to keep their feet on the ground and hunt large prey, whereas clouded leopards live in trees, leaping on their quarry, and cheetahs chase down antelopes at high speeds.
所有的猫科动物看起来都，好吧，像猫一样，不过狮子倾向于四脚着地，追捕大型猎物，而云豹则住在树上，从树下跃下抓捕猎物，猎豹则以高速追捕羚羊。
Paleontologists Marcela Randau and Anjali Goswami of the Natural History Museum in London did 3D analyses of 109 cat skeletons representing species with various hunting and living strategies.
伦敦自然历史博物馆的古生物学家马赛拉.兰道和安加里.戈斯瓦米对109种猫科动物的骨骼进行了3D分析，它们代表了拥有不同的捕猎和生存策略的物种。
They compared the vertebrae within each species and between species, as well as the limbs, shoulders, pelvises, and skulls.
他们把每种动物的脊椎进行了种内和种间进行了对比，还包括肢体，肩部，骨盆和头骨。
In all these cats, most of the spine looks similar.
在所有猫科动物中，大部分的脊椎看起来都是相似的。
Their lumbar regions have diversified, however, suggesting this region evolved independently of the rest of the spine and skeleton, Randau said last month at the second Joint Congress on Evolutionary Biology in Montpellier, France.
它们的腰椎区段则有所不同，表明该区段跟脊柱的其余区段和骨骼是独立进化的，兰道在法国蒙彼利埃举行的第二届进化生物学联合大会上说。
The size and shape of the lumbar vertebrae vary depending on what the cat does best.
腰椎区段的大小和形状的不同取决于这种猫科动物的特长。
"It's the lumbar region that really allows mammals to do all sorts of different things," Pierce says.
“正是腰椎区段真正使得哺乳动物可以做各种不同的事情，”皮尔斯说道。
On the downside, the more recently evolved parts of the back—the lumbar region in particular—are also the source of most back pain, Pierce says, so "maybe we also owe our ancestors for having back complications."
而不好的一面是，后来进化出来的背部部分—尤其是腰椎区段—也是大部分背痛的根源，皮尔斯说道，所以“也许我们的背部综合征也是来自于我们的祖先。”
对于脊椎的起源，朋友们有什么想法吗？欢迎给amber留言哦！
感谢关注
跟amber一起看世界
- END -
____
______
________
____
______
________