Today while making omelet an accident happened. I poured oil on tawa, then to spread it I broght the ladel upon it, the oil splashed and a big drop landed on my right hand middle finger. A beautiful blister formed, possibly it has some fluids inside. This will help my body fluids from oozing out, thus preventing dehydration and faster death. The top surface of blister is dry enough to prevent any bacterial growth, yet it traps fluids to act as a thermal mass in case the same part comes in contact with some hot substance once again. These fluids also provide a cradle or a packet of soup for my skin to grow, just like primordial life needed a soup of right stuff to evolve. I was bewildered. How did life learn to deal with fire?

Fire became common only after humans harnessed it, they somehow found a way to make it, and tame it. Even the Jarwas of Andaman who may have settled in the island 60,000 years ago are believed not to have the knowledge of fire. In that case how did the skin evolve to deal with hot substances? I was terribly confused.

You see for anything to evolve, lots of failures should happen. Imagine an earth where there is fire burning all the time, primitive animals ventured near it, some got burned, most of those which got burned died, but some evolved a mechanism of blistering, that is flooding fluids under the burned skin, they survived. So as these animals were attracted to the fire, and they made contact with it, even though fire hurts, only those which developed blisters had higher chance of survival, and we are the descents of them.

But where on earth such fire burns all the time? You may find volcanic magma, and hot springs. But animals usually stay away, they know fire hurts. Unlike us who cannot live without fire / extreme heat which we need for cooking (possibly the Jarwas, and Icelandic people can live without cooking. The Eskimos are good in eating healthy raw meat which digests better) , animals can eat raw food and live. If abundant fire was not available and was there only then and there as forest fires caused by lightning strikes or friction, how on earth did life evolve the art of forming blisters?

Thankfully the answer came from Wikipedia, it said:

A blister is a small pocket of body fluid (lymph, serum, plasma, blood, or pus) within the upper layers of the skin, typically caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection.

Ah friction! Friction causes heat, heat causes blisters. So as soon as life started to move fast, there would have been instances where it encountered friction, like sliding down on rock, like sandstone or something which causes extreme heat. This could have caused blisters in ancient animals. While running blisters could have formed on feet, hoofs were evolved to prevent that. This is very high chance of heating skin to cause damage than to wait for fire made by humans. A animal could have a fought and could have been pushed, so the one which had accidentally evolved the technique of blistering got less infection, survived better. So no need for nature to wait for humans to arrive and generate heat and burn forests to start selecting animals that can survive fire and heat better. If this blistering only started to evolve only 2 million years ago, (that is when intelligent human formed,) fire wounds by now would be one of the most fatal things as we wouldn’t have evolved sophisticated blistering as we see today.

Possibly there is a way to test this theory. Mostly aquatic animals may not be well enough to cope up with heat, and that too aquatic animals near the poles. If we can see how their skin reacts to heat, we may get an idea.