经济学人下载:恐龙行为 疯狂撞头的家伙

Science and technology
科学技术

Dinosaur behaviour
恐龙行为

Headbangers
疯狂撞头的家伙

Evidence of duelling dinosaurs
战斗性恐龙的证据

WORKING out how an extinct animal behaved when it was alive is tricky.
对于灭绝的生物来说，要研究出它们存活时的行为是很棘手，

But it is not always impossible,
不过也不是完全不可能。

as Joseph Peterson and Collin Dischler of the University of Wisconsin explained on October 17th to the Society of Vertebrate Palaeontology meeting held in Raleigh, North Carolina.
10月17日，在北卡罗莱纳州罗利市举行的古脊椎动物学会议上，美国威斯康星大学的约瑟夫·彼得森和柯林·狄斯勒就对肿头龙的习性做出了一些解释。

Pachycephalosaurs lived 65m years ago.
肿头龙生活在6500万年前。

As their name suggests, they had large, bony, domed heads.
正如其名称所说，它们有巨大的、高隆的头骨。

For years, it was assumed they used these to bash one another in the way that rams do now.
多年来，人们一直认为肿头龙用头攻击同类，就像现在的公羊一样。

Recently, though, a second suggestion has surfaced—that rather than for fighting, the domes were for show; the dinosaur equivalent of a peacock's tail.
不过最近有人提出另外一个假设：它们的大脑袋不是为了战斗，而是出于展示的目的—作用相当于孔雀的尾巴。

Dr Peterson and Dr Dischler put these two theories into a head-to-head competition.
彼得森和狄斯勒博士让这两种理论来了个头对头的正面对抗。

To do so, they studied 102 pachycephalosaur skulls, of various species.
为此，他们研究了102只不同品种肿头龙的头骨。

They found that 23 of these skulls had pits in them, and that these pits were similar both to each other and to those found in the skulls of living animals that bash each other with their heads.
他们发现其中23只头骨上有凹坑。这些凹坑彼此类似。而且现存的用头部撞击同类的动物中，头骨上的凹坑也与之类似。

That supported the head-butting theory. The clincher, though, came when they created computerised models of pachycephalosaur skulls and mapped the damage from each of their pitted specimens on to these virtual skulls.
这支持了头部冲撞理论。不过决定性的证据来自于他们用计算机模拟的肿头龙头骨。他们将每个有坑样本的损伤部位标注在虚拟的头骨上。

When they did this, they found that the pits were clustered—exactly as might be expected if they were the result of animals deliberately aiming at each other.
这样操作后，他们发现凹坑聚集分布，正如人们假设的那样：是肿头龙故意用头部攻击彼此的结果。

Intriguingly, they found two patterns of clustering.
有意思的是，他们发现凹坑有两种聚集图案。

Those pachycephalosaurs with highly domed heads had pits on both the fronts and the backs of their skulls.
那些不太隆起的头骨仅在前方有凹坑，而非常高隆的则前后都有。

Those whose domes were lower had them only on the fronts.
这证明了两种肿头龙攻击时的不同。

This suggests the two sorts of animal fought in different ways. Low-domes, it seems, simply charged at each other. High-domes did that too.
相对低隆的一种似乎仅向对方迎头冲撞。

But they also engaged in head-to-head wrestling of a sort that allowed them to get behind their opponents'skulls and do damage from the rear, in the way that modern bison do.
非常高隆的肿头龙除此之外还会采取头对头式摔跤法：能够碰到对方头骨的背部，从后面对彼此造成损伤，好比如今的野牛。

None of which proves that pachycephalosaurs did not strut their stuff with their domes as well, just as a stag will often show off its antlers before engaging in combat, in order to give a less well-endowed rival the opportunity to withdraw.
然而，两种图案都没有否定肿头龙自豪地迈步时也在炫耀他们的大脑袋。成年雄鹿就经常在战斗之前展示它的鹿角，为了使天生劣势的对手借机撤退。

But it does demonstrate that the domes were serious weapons, not mere fripperies of fashion.
不过这确实证明了高隆的头骨是很厉害的武器，而不仅仅是时髦的矫饰品。