This shows that the painters’ current diets did not need to include sea creatures. So the lack of sea creatures in paintings does not prove that the paintings don’t represent the painters’ current diets.

This raises the possibility that sea creatures might have appeared in paintings that are no longer around. So, the cave paintings could have been a description of the current diets of the painters, even if the paintings that remain no longer depict sea creatures.

The author never denied that the paintings could show land animals. The author’s position is that we’d expect to see sea creatures, too. So, the presence of land animals in the paintings doesn’t undermine the author’s argument.

This raises the possibility that the painters did not need to eat sea creatures, contrary to the author’s assumption. The painters might have been able to travel to the islands while eating preserved meat from land animals.

This shows that the author’s assumption that the painters needed to cross the islands and eat sea creatures is wrong. The painters could have been done by inhabitants of the islands who may not have needed to eat sea creatures.