Misunderstanding evolution

By November 25, 2017Science, Society

Often you will hear a creationist, or simply an ignoramus ask: “If we evolved from apes how come there are still apes around?” I have had this question asked of me a couple of times over the years, once by a creationist and once by someone who was simply ignorant of most of biological science. Asking this question shows a singular lack of understanding of how evolution works. It makes as much sense as asking: “If I was born of my mother how come she is still around?” These people seem to think that all the species of ape coalesce into one species and morph into Homo sapiens, which illustrates only their profound ignorance, or in the case of creationists, willful ignorance.

First, let me explain what apes are. They all belong to the Superfamily Hominoidea and are a group of tailless anthropoid primates native to Africa and Southeast Asia. There are two families within that superfamily. The first is the Hylobatidae, or lesser apes, which includes about 16 species of gibbon belonging to four genera (Hylobates, Hoolock, Nomascus, Symphalangus). The second family is ours, the Hominidae, or great apes, which includes three species of Orangutans (genus Pongo), two species of Gorilla (genus Gorilla), two species of chimpanzees (genus Pan), and one species of human (genus Homo). So, there is a considerable diversity of apes on the planet, and now there is only one species of human.

What we know about the evolution of the Hominidae is extremely patchy. This is because they are rarely fossilised, because they live in jungles, woodlands and grasslands, and only fossilise when they are covered over by sediment before the bones disintegrate, in rivers, lakes, swamps and in caves. Despite this, there are several thousands of specimens, and we have a reasonable idea of the diversity of early hominids2,3.

The most closely related extant genus to ours is that of the chimpanzee and bonobo (i.e., Pan). Several studies on the genetics of Homo and Pan clearly show the close relationship between the two with about a 99% commonality in genetic makeup. Based on what we know about genetics and how DNA changes over time, this indicates that the last common ancestor lived about 6 million years ago. Chimpanzees, bonobos and humans have all evolved from that last common ancestor (hence the name)4,5. What that last common ancestor was really like we can only infer. However, it was not Pan troglodytes (chimpanzee) nor Pan paniscus (bonobo). It may have looked like something intermediate between Homo and Pan, perhaps something like an Australopithecus2, but we may never know. That is one of the things that distinguishes science from religion. Science is not afraid to say ‘we don’t know’, whereas religion says ‘we know the answer, now what was the question?’

Sources

  1. https://en.wikipedia.org/wiki/Ape
  2. https://en.wikipedia.org/wiki/Australopithecus
  3. https://en.wikipedia.org/wiki/Homo
  4. https://en.wikipedia.org/wiki/Hominini
  5. https://en.wikipedia.org/wiki/Chimpanzee–human_last_common_ancestor

 

One Comment

  • Anonymous says:

    This is great! Only issue I have is “What the common ancestor was like we can only guess at.” Fortunately, the outgroup criterion allows for effective inference, while not proving. For example, gorillas (proximal outgroup) and chimps both are knuckle walkers, so we can already infer the last common ancestor of humans and chimps was most parsimoniously a knuckle walker. Other fossil and trace fossil evidence within our own lineage have provided details of the evolution of bipedal locomotion from this last common ancestor. This inference of an ancestral character state is performed for individual character states with two or more alternate states, “present” vs. “absent” or “A” vs. “C” vs. “G” vs. “T”. Gorillas and chimps might both have “G” vs. “T” in humans allowing an inference of “G” in the last common ancestor. Yes, the “G” in chimps could have evolved by convergent or reversal mutation to match the gorilla, but this would be less parsimonious than inferring that a single event occurred, unique in the human lineage. This method, known as character optimization, is done independently from the method that provided the phylogenetic tree estimate. I provided some examples to emphasize that it is a relatively modest character-by-character procedure that is unlikely to produce a reliable composite estimate of the last common ancestor. Another limitation is that a particular character state optimization can be either unambiguous or ambiguous on a particular tree.

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