Human evolution was a straight march of progress
An old model or guideline was retired in favor of a new one.
TaughtThe famous parade: an ape stands up, becomes Australopithecus, then Homo erectus, then Neanderthal, then us. One species at a time, each better than the last.
NowHuman evolution is a branching bush with many species coexisting. At times several kinds of human shared the planet, and the discovery of Homo floresiensis in 2004 made that impossible to ignore.
What actually happened
The march-of-progress illustration first appeared in a 1965 Time-Life book and became the most successful science graphic ever made, which is unfortunate because its central message is wrong. Evolution is not a ladder toward a goal, and Homo sapiens is not the destination.
The fossil record now shows multiple hominin species living at the same time in the same regions. Homo floresiensis, the roughly one-meter-tall species found on the Indonesian island of Flores in 2004 and nicknamed the hobbit, survived until perhaps 50,000 years ago. Homo naledi was described from South Africa in 2015. Neanderthals, Denisovans, and Homo sapiens all overlapped and, as we now know, interbred. As recently as 100,000 years ago there were probably at least five kinds of human alive. The strange fact requiring explanation is not our ascent. It is why we are currently the only one left.
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Sources
- Nature: A new small-bodied hominin from Flores, Indonesia (Brown et al., 2004)nature.com
- Smithsonian: Human Origins Programhumanorigins.si.edu
Who was taught this
Still standard through 2008, so anyone who finished school between 1950 and 2004 learned the earlier version.