Humans are practically defenseless. Why don't wild animals attack us more?

It's a 19th Century myth that humans' sense of sight and smell is weak compared to the rest of the animal kingdom.

The thing that probably stops most predators from killing us, over the course of our evolutionary history, is that we see them before they see us and move or make lots of noise. Predators then have to exert more energy hunting us down and probably fight a whole group of humans.

In terms of color perception, humans are near the top in mammals. One mammal with better color perception than us is the tetrachromatic reindeer (who are also some of the only mammals with ultraviolet color perception and red-green perception; some dichromatic rodents do have UV perception from their blue rod). Most mammals do not have more than two color rods in their eyes.

Having better color perception allows us to see color patterns that are invisible or much more subtle to other animals. Almost every mammal is a dichromat with two color rods, but humans and a handful of our closest Ape relatives are trichromats. To dogs, deer, lions, and a portion of humans, the distinction between green shades and red shades is much more subtle:

The notion that human visual perception is only good because our brain is so good is Cartesian, Freudian, and Victorian. No matter how big our brain was, if our visual acuity was worse, we would see fewer patterns in the first place.

If you take a dog on a walk, and you are paying attention to the world around you, odds are you will see an animal way before your dog does. Your dog will smell an animal before you do though. The only time my dogs have ever sighted an animal before me I was on my phone, or the animal was low to the ground (e.g., under a car) and I couldn't see the animal at human-height.

We aren't blind-deaf disembodied brains compared to other animals. Human eyes are very powerful and decrease the likelihood of being ambushed. They further decrease the likelihood of a predator picking off a human alone by giving a human ample time to raise the alarm.

If Zebras and Antelope had as good of eyesight as humans, Lions would probably starve to death. The amount of time between each feeding would increase to the point that they would be exerting more energy to kill a zebra than they gain from eating one.

The eyesight of other mammals is, on average, poor. Hunters go off in the woods wearing orange vests so that other hunters don't accidentally shoot them, and they still sneak up on deer.

Yeah she has a rifle, but a human would see her beyond the range of a typical rifle (which is the point of her attire).

Reference:

Hayes, S., Boote, C., Lewis, J., Sheppard, J., Abahussin, M., Quantock, A. J., ... & Meek, K. M. (2007). Comparative study of fibrillar collagen arrangement in the corneas of primates and other mammals. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology: Advances in Integrative Anatomy and Evolutionary Biology, 290(12), 1542-1550.

Campbell, F. W., Maffei, L., & Piccolino, M. (1973). The contrast sensitivity of the cat. The Journal of Physiology, 229(3), 719-731.

Brian Collins PhD candidate in linguistics at U of Queensland Updated July 18

_Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic