Gorilla Feet

I promise every post in Chicago won't be about the apes at the zoo, but there will probably be a few more after this one too!

This is a gorilla foot:

Gorilla Foot

I was able to get such a great picture because the gorilla was sleeping with his foot up on the glass.  I touched the glass after I took this pictures, and it appeared to be about 1.5 inches thick.  After seeing the adult male gorilla kick the door in his enclosure a few days ago, I'm hoping that glass is thick enough!  That gorilla is massive and extremely strong. 

Gorillas are usually fairly mellow, and they seem to have less intense social interactions than chimpanzees do.  They do engage in grooming behavior, aggression and play, but their interactions are much less constant than the chimpanzees'.  They are vegetarian, mostly forest floor dwelling and less active in general than chimps.

Gorilla's forelimbs are massive and long.  Their arms are about six times stronger than ours.  Their legs are much smaller, though still strong.  Even though they spend lots of time on the forest floor, they are still very good climbers, and they use their arms to amble around the branches and vines with ease. 

Gorilla's feet have opposable thumbs.  They are good at grasping things - branches or food, but they are not good at walking upright.  Our feet have all toes pointing forward, which is great for bipedal locomotion, but have you ever tried to pick up anything with your toes?  Not easy.

Beyond shape, there are many similarities in our feet and gorillas'.  First, scroll back up to the picture and notice the prints.  I can't call them fingerprints, because they are on the sole of the foot, but we have these too.  We have prints all over the bottom sides of our fingers, palms, toes and soles, and so do gorillas.  These prints are due to ridges in the subskin (dermis) where it attaches to the upper skin (epidermis).  The ridges and valleys allow for more contact between the two layers, which reduces separation of the layers from friction.  What that means in everyday English is that it reduces the incidence of blisters.   

Next, notice the nails.  These guys have fingernails and toenails, not claws.  Nails are good for manipulation of plants and small structures, and they protect the fingers from stomping or insect bites, but they're not good for ripping flesh.  Since gorillas are herbivores and big and strong, they don't need claws for food or defense, so they have nails.  We are not entirely herbivores, but we use tools to catch our animal prey, so we don't really need claws either.  We do, however, need to manipulate small items, and nails are useful for that.

Gorilla and human feet are homologous structures, meaning they have the same evolutionary origin, and have developed from the same bone and muscle pattern.  Since gorillas and humans separated on the evolutionary tree a long time ago (well, in evolutionary time, not so long ago) and have adapted to different environments, our feet have evolved in slightly different directions too.  Scientists think the evolutionary ancestral foot to humans and gorillas was more like the gorilla one, though probably smaller and more hand-like.  Primate ancestors were even less bipedal and more tree-dwelling.