13.1: Chapter Introduction

Early humans suffered from predators just as other primates suffer still. Eventually, though, they developed spears longer than the longest teeth and became one of the top predators on land. Even if they did not eat sabre-tooth tigers, they were able to kill them. We know from vivid paintings on rock walls in the protected shelter of caves that our ancestors at least fancied themselves as hunters (Figure \(\PageIndex{1}\)).

Figure \(\PageIndex{1}\) Hunter and hunted.

Humans are now the dominant large vertebrate on the planet. But on all the continents beyond Africa, large vertebrates were prominent in the ecosystems before our ancestors arrived. In Africa many remain, coevolved with humans and perhaps wiser to our ways. Elsewhere, however, they had little fear when our ancestors arrived (Figure \(\PageIndex{2}\)).

Figure \(\PageIndex{2}\) Artist’s conception. The Moa had no clue that the diminutive primate was aiming a barb that would shortly pierce its heart. Unafraid and then gone.

The reasons behind the extinction of so many megafauna are controversial. Archeologist Haynes and others believe humans are responsible. Archeologist Grayson and others blame climate change, though animals had been through many glaciations and deglaciations before. Mammalogist MacPhee and virologist Marx postulate a virulent “hyper- disease” brought by humans. And geologist Kennett and colleagues assign a comet impact as the cause—an interesting theory, as some major human hunters disappeared at about the same time as the larger mammals.

Figure \(\PageIndex{3}\) The remaining mass of Earth’s megafauna lives in the sea.

In any case, when something extreme happens, several causes may be working in concert. We do know from historical records that only about one human lifetime ago our predecessors in North America hunted bison almost to extinction (Figure \(\PageIndex{3}\)). Now the large remaining populations of megafauna are in the seas. What is their fate?