Evolution would've given us infrared eyesight

The body temperature of an active Viper is only about 5 degrees less than that of a human. I doubt that would be sufficient to make it practical or not.I suspect the real answer lies in the nature of the infrared sensing pits. As you noted, snakes don't "see" infrared with their eyes, but with specialised organs. Why is that?I think there are two likely reasons:1. Thermoreceptors need a system of cooling; putting such a system into the retina would considerably degrade visual quality.2. Photoreceptors work via certain pigments that are modified (bleached) by incoming photons. I'd hazard a guess that the lower energy levels of infrared photons aren't high enough for this method to function efficiently.

Why would it? The need for thermoreceptors is far less in mammals; we already have advanced thermoregulation. Thermoreceptors in snakes, you see, are used more often for finding warm spots in which to bask than to catch mice, and it is doubtless this use that propelled their earlier evolution.Edited by Mr Jack, : Whoops! Had written photoreceptors when I meant Thermoreceptors.

Ever wondered why we see in that range?The answer is that it's a range that is largely unabsorbed by the atmosphere. As you move into the infrared or the ultraviolet, you rapidly start getting into regions of much higher absorbtion. In fact, the IR detection of snakes isn't the "near"-IR but two windows someway distant at frequencies about 6-10 and 20-30 times lower which are also able to travel through the atmosphere.

I think you mean 750nm and 1000m.Edited by Mr Jack, : No reason given.Edited by Mr Jack, : No reason given.

More details, please?Infrared is a very wide band of the spectrum; if you mean near infrared then, yeah, you're certainly right but it's not of any great significance - it won't let you track footprints by their heat impression or anything.

It's generally considered unlikely that the first organisms were RNA (too complicated a molecule). It's more likely that they were self-replicating polypeptide chains (proteins, basically) but your basic point: the first life was a self-replicated molecule with no seperate genetic material stands.