早期哺乳动物也有社会生活?

This is Scientific American's 60-second Science, I'm Christopher Intagliata.

这里是科学美国人——60秒科学系列，我是克里斯托弗·因塔利亚塔。

Seventy-six million years ago, a group of small mammals huddled in a burrow in what’s now Montana.

7600万年前，一群小型哺乳动物挤在现在蒙大拿州的一个洞穴里。

They were good diggers—most likely furry—and petite.

它们很擅长挖掘——很可能是毛茸茸的——而且是娇小的。

“They could sit comfortably in the palm of your hand.

“它们可以容易地坐在你的掌心。

I mean, if you saw them running around today, you’d think it’s a small rodent—a chipmunk or mouse.”

我意思是，如果你现在看到它们跑来跑去，你会认为它们是一种小型啮齿类动物——花栗鼠或老鼠。”

Lucas Weaver is a mammal paleobiologist at University of Washington.

卢卡斯·韦弗是华盛顿大学的哺乳动物古生物学家。

These subtle creatures didn’t belong to any of the three main mammal groups on the planet today—which are the placental mammals (like us), monotremes (like the platypus) and marsupials (like koalas and kangaroos).

这些小动物不属于今天地球上的三个主要哺乳动物群体——胎盘哺乳动物(像我们)、单孔目哺乳动物(像鸭嘴兽)和有袋哺乳动物(像考拉和袋鼠)。

Instead they belonged to another, now extinct group called the “multituberculates.”

相反，它们属于另一个现已灭绝的群体，称为“多瘤齿兽类”。

“They have these really bizarre molars with multiple bumps, which is where they get their name. Multituberculate. just means ‘many bumps.’”

“它们的臼齿非常奇怪，有多个隆起，这就是它们名字的由来。多瘤齿兽类就是‘很多隆起牙齿’的意思。”

Weaver and his colleagues have studied the fossilized skulls and skeletons of these animals, dug up in Montana, and they’ve given them a name: Filikomys primaevus (friendly or neighborly mouse).

韦弗和他的同事们研究了蒙大拿州挖掘出的这些动物的头骨和骨骼化石，并给它们起了一个名字:Filikomys primaevus(友好或睦邻老鼠)。

The details are in the journal Nature Ecology & Evolution.

详情发表在《自然生态与进化》杂志上。

Weaver says drought or climate change may have killed the animals, though it’s hard to be sure.

韦弗说，干旱或气候变化可能杀死了这些动物，尽管很难确定原因。

But the critters were fossilized together in ways that suggest they sought out each others’ company.

但这些动物以一起变成化石的方式表明它们互相寻找伴侣。

That’s a big deal because it’s commonly thought that social behavior didn’t arise in mammals until after the death of the dinosaurs, 10 million years after these small critters hung out together.

这是一件大事，因为人们普遍认为，直到恐龙灭绝后，哺乳动物才出现了社会行为，那是在这些动物聚在一起的1000万年之后。

“The narrative, for decades, has been that mammals living during the time of dinosaurs were mostly solitary ratlike creatures scuttling in the night under dinosaurs.

几十年来，一直有这样的说法，即生活在恐龙时代的哺乳动物大多是单个的鼠形生物，夜间在恐龙的身下急促奔跑。

And so the fact we’re finding these multituberculate mammals—a totally unrelated and ancient group of mammals—exhibiting social behavior means this was probably not uncommon among these early Mesozoic mammals.

因此，我们发现这些多瘤齿兽类动物——一种完全无亲缘关系的古老的哺乳动物群体——表现出社会行为的事实意味着，这在这些早期中生代哺乳动物中可能并不罕见。

And it kind of changes the narrative that(of) sociality is somehow unique to placental mammals.”

它改变了关于社会性是胎盘哺乳动物独有的说法。”

Even today, social behavior is relatively rare among mammals.

即使在今天，社会行为在哺乳动物中也相对少见。

But these findings suggest the need for company in some mammalian species is an ancient evolutionary invention.

但这些发现表明，某些哺乳动物需要同伴是来源于古老的进化。

Thanks for listening for Scientific American's 60-second Science. I'm Christopher Intagliata.

谢谢大家收听科学美国人——60秒科学。我是克里斯托弗·因塔利亚塔。