"We seem to live in a hazardous time, drifting along here through space. Nobody knows just when we begun, or how far we've gone in the race."

-- Benjamin Franklin King, Jr. [source: WorldofQuotes.com]

The 19th century American humorist King may have been unsure of his origins, but that era contributed to knowledge of the human race. Highlights included:

• Early 1800s. French naturalist Jean Baptiste Lamarck, after studying fossils, argued that organisms changed their behavior in reaction to transformations in their environment, leading to changes in physical structure (such as the "stretching" of a giraffe's neck to reach tree leaves).
• Mid 1800s. Alfred Russel Wallace and Charles Darwin were British researchers who concurrently, but separately, developed similar ideas about evolution: Although the population of any species has much in common, there are individual differences that might be advantageous to survival. If those individuals reproduce, the differences become traits of future generations.
• Late 1800s. Ernst Haekel was a German scientist who believed the initial growth of an embryo matches the earliest, single-cell life forms. He called this "ontogeny recapitulates phylogeny." Unfortunately, Haekel modified some of his data to conform to his proposal. [source: University of California, Berkeley, O'Neil]

Through peer review, discovery and revision, scientists have defined and refined evolution (inherited changes that occur over many generations of a population). They have traced the evolution of flora, fauna and hominids (humans and their ancestors). The following are 10 important discoveries in human evolution.