Remember back sixty-five million years ago when the 10-kilometer bolide struck the Yucatan Peninsula, at Chicxulub in Mexico? Sure you do, it’s like yesterday, it’s when the dinosaurs went extinct. There was worldwide devastation which is marked worldwide in the soil by the iridium rich K-T boundary layer. It is the cloud of dust that settled out after the impact and it can be seen in many places where erosion has exposed it. Many species were wiped out by the cloud of finer particles which remained in the atmosphere and prevented sunlight from reaching the ground. The plants didn’t grow without sunlight and without the plants growing for a year or more the animals which eat plants died, and soon the animals which eat plant-eating animals died too. But why did our ancestors survive and reproduce when so many others failed to survive or thrive? Obviously our progenitors survived or we wouldn’t be here, but why ours and not theirs? My post Why the human lineage survived the last extinction event, covers the reasons for our survival in some detail, but in brief it was because, while all animals living in the tropical and temperate regions were wiped out by lack of sunlight, those living in the polar regions were pre-adapted to long dark winters. Those living under the soil, like moles, were especially likely to survive very long winter conditions, because part of their food source was underground. That is why I speculated that moles were in our lineage and not temperate or tropical squirrels.
Today in the news there was an article reported in Yahoo, Earliest mammals sniffed their way to smarts; it was based on an article in AAAS Science, Evolving Large and Complex Brains by R. Glenn Northcutt. What is interesting in this article, relative to the arctic period of our postulated past, is that the small mouse-like animals reported upon in the article had brain regions suggesting good smell abilities, and good surface touch sensors linked to hairs. Other analysis showed these animals were eating insects, worms and grubs. Their abilities were honed to improved sensitivity to things touching their body hair, which helped these creatures sense their environment when they were scurrying under leaves. for example.
The exact creatures being studied may not have been moles as we know them, but these animals already adapted to living on the ground under leaves and hiding from predators by being very close to and even under the ground would need very little adaptation to become mole-like creatures living primarily underground. It was these animals, some of whom found themselves living in and adapted to the arctic regions, who would have been most likely to survive the K-T extinction event. After the ecological slate was wiped clean in the tropics, there would have been myriads of opportunities for these survivors from the arctic to find new niches. And it is known that some of our early ancestors were quick to ascend into the trees. This can happen very quickly, as has been observed in Israel where there were no squirrels in a remote area when some trees were brought in and in a few years the local rats took over the habitats in the trees that are normally limited to squirrels. These animals are still rats, but if they were isolated for a very long time they would behave even more like squirrels.
Evolution can proceed quickly when there are ample rewards to be found with a little learned adaptation, and when the creature can survive with that learned adaptation any physical and genetic improvements can then enhance the learned skills with natural genetically enhanced abilities and speciation will eventually occur.
Here is a reason for me to appreciate the mole hill in my back yard.