One of my favorite days of the year is here: Darwin Day! Happy birthday Uncle Charles... 198 years young, and many more to come!

For those of you questioning humanity's status as a primate and our relationships to other members of our family tree, here are a few things to think about-

Consider the primate form: all primates, including humans, have five digits on each hand and foot. We all share the same basic physical structure.

Look at the genetics: we share 94%+ of our genome with chimpanzees.

Look at the practical use we've made of the physiological similarities between humans and other primates: we're so alike, clinical tests are conducted using chimpanzees, apes and other primate members as stand-ins for for humans during drug development. A wide range of treatments and cures modern humans take for granted, such as the polio vaccine, were developed and tested on monkeys. Humans and other primates are afflicted by many of the same or similar diseases.

When looked at rationally, a mountain of other examples all point to our shared evolutionary path. Human embryos have a tail which is absorbed during development. Just as other tailless primates, human adults have a tail bone, the vestigial remnant of what swung behind our ancestors. The upright gait is still in development, giving rise to knee and lower back problems in many humans. Apes have a limited ability to learn human language. Chimpanzees laugh... they also use tools.

If you're someone who has been taught to consider evolution a preposterous theory with no basis in fact, I urge you set aside your bias and read Uncle Charles with an open and rational mind. All of his writings are available on the web.

A passage from The Origin Of Species:

Numerous instances could be given of characters derived from parts which must be considered of very trifling physiological importance, but which are universally admitted as highly serviceable in the definition of whole groups. For instance, whether or not there is an open passage from the nostrils to the mouth, the only character, according to Owen, which absolutely distinguishes fishes and reptiles—the inflection of the angle of the lower jaw in Marsupials—the manner in which the wings of insects are folded—mere colour in certain Algæ—mere pubescence on parts of the flower in grasses—the nature of the dermal covering, as hair or feathers, in the Vertebrata. If the Ornithorhynchus had been covered with feathers instead of hair, this external and trifling character would have been considered by naturalists as an important aid in determining the degree of affinity of this strange creature to birds.

Related: Charles Darwin Has A Posse