A recent study has provided clues to predator-prey dynamics in the late Pleistocene era. Researchers compared the number of tooth fractures in present-day carnivores with tooth fractures in carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Brea tar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher than those in the present-day species.

In considering possible explanations for this finding, the researchers dismissed（负评价） demographic bias because older individuals were not overrepresented in the fossil samples. They rejected（负评价） preservational bias because  a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits. They ruled out（负评价） local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible（正评价即TS） is behavioral differences between extinct and present-day carnivores-in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species（TS）. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.

我不是很清楚，这里的breakage 不是磨损的意思吗？

breakage磨损度 extinct > present 是要解释的现象

而后来的prey availability was low and intense competition, high rate of carass theft是什么意思？ 供怪兽们可捕食的量低，竞争高, 源于捕食者的密度造成的尸体争夺率高 这些说明了什么？ 我不觉得这些可以造成extinct的怪兽breakage > present的怪兽的啊？

还有这里的a total absence of breakage 是什么意思？ 为什么这个可以rejected preservational bias ?  preservation bias是什么偏差？

我在这篇文章进入混沌状态好久，请大家帮帮忙，多谢了！

不是很理解absence of breakage是 什么意思？ “没有磨损”？

保存偏差 的 排除 是因为 两种extinct species 的total absence of breakage证明了化石碎片不是由于坑的磨损？

你所说的consumption含义了
远古怪兽的牙 之所以被磨损的如此严重，主要是由于它们的生活饮食习惯
 
远古怪兽吃东西 连骨头一起吃——费牙
现在的兽兽吃东西文明一些——吃肉就好了
 
而造成以上饮食习惯的原因是：
 
either
1. 吃的东西少（prey low）
or
2. 捕食兽兽密度大造成了 intense competition over kill 和 high carcass theft 对么？

  competition 是 predator 发出的还是 prey 发出的？ 为什么？