What is the prehistoric overkill hypothesis, and what evidence ...

[vicotolentino]

What is the prehistoric overkill hypothesis, and what evidence supports overkill as the reason for the
  Pleistocene extinctions? What is the alternative hypothesis? What will be an ideal response?

Question 2

What was the first line of evidence that the Cretaceous Mass Extinctions were caused predominantly
  by a large meteorite impact? What will be an ideal response?

[Briannahope]

Answer to Question 1

The hypothesis states that human hunters were responsible for the extinctions. Extinctions occurred
mostly on North America and affected mostly large terrestrial mammals, whereas previous extinctions
affected many other kinds of organisms. The alterative is that rapid climate change at the end of the Ice
Age killed off the large mammals because they could not adapt to the warmer climate.

Answer to Question 2

An abnormally high concentration of iridium was discovered in a 2.5 cm-thick clay layer in Italy,
which was followed by many more discoveries of high iridium in rocks that age. Iridium is common in
some meteorites, and the high concentration could be explained by a large meteorite impact.