科学美国人60秒 早期哺乳动物也会有社交生活（在线收听）

Seventy-six million years ago, a group of small mammals huddled in a burrow in what’s now Montana. They were good diggers—most likely furry—and petite.

七千六百万年前，一群小型哺乳动物挤在现在的蒙大拿州的一个洞穴里。它们擅长挖掘——长着毛——而且身材娇小。

“They could sit comfortably in the palm of your hand. These things, if you saw them running around today, you’d think it’s a small rodent—a chipmunk or mouse.”

它们可以舒服地坐在你的手掌上。如果你现在看到它们跑来跑去，肯定以为是小老鼠——花栗鼠或老鼠。”

Lucas Weaver is a mammal paleobiologist at University of Washington.

卢卡斯·韦弗是华盛顿大学哺乳动物古生物学家。

These little 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).

这些小动物不属于当今地球上三种主要哺乳动物——胎盘哺乳动物(例如我们)、单孔目哺乳动物(例如鸭嘴兽)和有袋动物(例如考拉和袋鼠)。

Instead they belonged to another, now extinct group called the “multituberculates.”相反，它们属于另一种现已灭绝的类群，叫做“多瘤齿兽”。

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

“它们有非常奇怪的臼齿，上面有许多凸起，这也是它们得名的原因。”Multituberculate。只是意味着‘很多颠簸’。

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).

韦弗和同事研究了在蒙大拿挖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(友好或邻居老鼠)。

The details are in the journal Nature Ecology & Evolution.

研究详情发表在《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. But the critters were fossilized together in ways that suggest they sought out each others’ company. 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.

韦弗说，虽然很难确定，但干旱或气候变化可能是导致这些动物死亡的原因。但这些生物一起被石化表明它们在寻找彼此的陪伴。这是一件大事，因为人们普遍认为哺乳动物的社会行为是在恐龙灭绝后才出现的，在这些小动物一起生活了1000万年后才出现。

“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. And so the fact we’re finding these multituberculate mammals—a totally unrelated group of mammals—exhibiting social behavior means this was probably not uncommon among these early Mesozoic mammals. And it changes the narrative that sociality is somehow unique to placental mammals.”

几十年来，一直有一种说法是，生活在恐龙时代的哺乳动物大多是夜间在恐龙脚下独自奔跑的鼠形动物。事实上，我们发现这些多瘤哺乳动物——一组完全不相关的哺乳动物——表现出社会行为意味着在这些早期中生代哺乳动物中，这可能并不罕见。它改变了社会性是胎盘类哺乳动物特有的说法。”

Even today, social behavior is relatively rare among mammals. But these findings suggest the need for company in some mammalian species is an ancient evolutionary invention.

即使在今天，哺乳动物的社会行为也相对少见。但这些发现表明，某些哺乳动物物种是古代文明进化的结果。