Which one of the following was not an important challenge to the initial acceptance of Darwinian evolution following publication of the Origin of Species in 1859?

1)Evidence of extinction: the finding of extinct fossil species suggested that organsisms are not well adapted to their environments.

2)All of the above were important challenges.

3)A suitable model of inheritance: Mendelian genetics was unknown to science and it was unclear how adaptive variation could be maintained within populations.

4)A source of new genetic variation: the process of mutation was unknown and it was unclear where new adaptive variation would come from.

5)The age of the earth: initially thought to be too you to permit the diversification of life via evolution.