European philosophers and scientists have debated questions like these for more than three centuries.From the pre-evolutionary musings of sixteenth century Dutch anatomists like Nicolaes Tulp and eighteenth century naturalists such as Carl Linnaeus, to the father of evolutionary biology, Charles Darwin, and his successors, Western scholars have long pondered where among the living primates humans belong.

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The careful and detailed dissections of Great Apes and humans done by 'Darwin's bulldog', T. Huxley, in the late nineteenth century seemed to reveal that gorillas and chimpanzees were physically more alike than either species was to humans.

This also squared with the view that humans were very distinct from the other African Apes, having evolved for longer, and perhaps at a faster rate, to obtain highly distinctive features like our upright posture, bipedal locomotion and big brains.

It was even suggested that humans had split from a common ancestor with the African apes by about 30 million years ago, making our evolution a very long process indeed.

Coincidentally, at the time Ramapithecus was being touted as the first human ancestor, pioneers of the nascent field of molecular biology were beginning to compare blood proteins among different mammals, including humans and apes, to study their evolution.

By comparing the ratio of potassium to argon, scientists gauge how long this natural clock has been ticking.

The age of volcanic rock and ash can be "pinpointed" to within roughly twenty thousand years -- a mere moment in Earth's 4-billion-year history.

With the advent of ancient DNA sequencing, we can even study clocks in extinct species and get a handle on whether its ticking rate has changed over time.

These first molecular clocks suggested humans and gorillas had separated only around 11 million years ago, not 30 million as suggested by fossils like Ramapithecus.

A light rain then turned the ash into a sort of cement that recorded thousands of tracks of antelopes, rhinos, guinea fowl, and monkeys, as well as the footprints of our ancestors.