What sets Homo sapiens apart from other animals? Among other things, our chins do. That piece of bone sticking out from your jaw is somewhat of a mystery - one that's inspired a diversity of wild theories to explain its purpose, according to a paper published this month in Evolutionary Anthropology.

The author of the paper dismisses a number of these explanations, such as the possibility that the chin serves as a sexual signal (such traits usually only appear in one sex - like the mane of a male lion). Another proposal is that the chin acts to protect your throat - an idea the paper's author also shoots down, because for this to be a substantial advantage, humans would have to be constantly punching each other in the face.

So the mystery rem ...

Lungs have 'taste buds' which can detect bitter-tasting compounds, although aren't connected to the brain! The taste receptors in the lungs are the same as those in the mouth except they are not found in clusters and do not send any signals to the brain.

The bones of the male human face evolved their shape to withstand fistfights, according to a recent scientific study.

This is the semi-transparent eyelid of the red-eyed tree frog, Agalychnis Callidryas. Frogs aren't the only creatures with 'third eyelids' that keep their eyes moist without blocking vision completely. Sharks, cats, crocodiles, polar bears and camels have them too.

Pupula duplex - commonly called double pupil - is a rare medical condition, in which one's eye or eyes has two pupils.

Read more: Pupula duplex

The harsh desert environment is known for its scorching temperatures and scarcity of water, making it a challenging place for most creatures to thrive. However, amidst this seemingly inhospitable landscape, the kangaroo rat stands out as a remarkable example of nature's ingenious adaptations. These small rodents have not only managed to survive but thrive in the desert with virtually no drinking water. The secret to their survival lies in their unique physiological features, particularly their kidneys' specialized structure.

Generally, the majority of water reabsorption in the kidneys occurs in the loop of Henle (see illustration). This structure is responsible for the reabsorption of water and essential ions from the urine back into the bl ...

A viscous fluid made out of citrate and water is what gives our bones flexibility. The gooey fluid is trapped between the tiny crystals of calcium phosphate that form our bones, absorbing shocks and allowing movement. Without this fluid the crystals fuse together and become less flexible and brittle.