About this video from PBS, “There Was No First Human,” recommended by Jerry Coyne, it’s hard to know where to begin. The host’s attitude? The snarky graphic “It’s Okay to Be Smart”? Well, let’s just stick to the factual errors. There is no continuous stack of photos documenting our unbroken history all the way back to our “fishy ancestor” Tiktaalik. It is true that fossils are snapshots of the past. But the idea of continuous gradual change is an inference not documented by the fossil record. Any paleontologist can tell you so.
That idea is based on Charles Darwin’s view that evolution must be the result of gradual slight variations among populations that were selected over time, resulting in a slow, invisible process of change rather than sudden transformation, such as speciation. Richard Dawkins, whose book The Magic of Reality: How We Know What’s Really True is mentioned in the video, is one of the more recent spokesmen and true believers for this view.
However, it is not universally held by evolutionary biologists. In what follows I will write strictly as an evolutionary biologist would, one who doubts the view advanced in the video.
In 1977, Gould and Eldredge, in a now famous paper called “Punctuated Equilibria: The Tempo and Mode of Evolution Reconsidered,” proposed that this idea of gradualism “expressed the cultural and political biases of 19th century liberalism. … We think that it has now become an empirical fallacy.”
They argued that the fossil record is more aptly characterized as one where species show long periods of stasis — remaining essentially unchanged — followed by a sudden change in form, or speciation, sudden at least in geologic terms. Now, to be fair, they weren’t arguing for anything like sudden creation, but they were arguing for rapid change (geologically speaking) in small isolated groups.
How rapid? They argue that in order to explain the rapid change we observe in something like whale evolution, or human evolution, there must be rapid genetic change at the time of speciation. If the incipient species were prevented from mating with the older form, change could be quite rapid. These ideas, by the way, were not new to the evolutionary biologists of the time. It was only later that scientists came to prefer the current model, one where populations diverge by a process of gradual differentiation as the mode of speciation (what goes around comes around).
Now I return to a design perspective. The sudden appearance of new species is true for many, many kinds of animal and plant life, both major and minor. To name a few where whole groups appeared with no apparent predecessors there are: The sudden appearance of insects, then winged insects, of bats, of flowering plants, of major phyla at the Cambrian explosion, and of the genus Homo. (By the way, Homo erectus looks pretty human to me, but that’s just my personal opinion.)