10TH JUNE 2022
Dear Friend of Darwin,
Charles Darwin appreciated one of the most compelling arguments in favour of his theory of evolution by means of natural selection was just how much apparently unrelated stuff it explained. In one letter, he asked an unconvinced colleague to consider the ‘large body of facts in Geographical Distribution, Geological Succession, & more especially in Classification, Homology, Embryology, [and] Rudimentary Organs’ that his theory explained. After years of research, he had written about each of these subjects in On the Origin of Species.
Species’ classification—what we would now call taxonomy—was a particularly interesting example. Expert taxonomists had categorised species according to similarities in their physical structures—that is, in their morphologies. Darwin realised the groupings contemporary taxonomists had come up with actually tended to reflect how closely the species were related to each other through genealogical descent. He rightly pointed out that genealogical descent was the correct way to classify species—which is exactly how modern taxonomists try to classify them.
As Darwin also pointed out, the idea that species were related through genealogical descent also threw considerable light on their geographical distributions. For example, all the many species of living and extinct kangaroos are or were indigenous to Australia and New Guinea because they all evolved from a common ancestor that lived in that region. The same goes for the rheas of South America, the finches of the Galápagos Islands, and all manner of other groups of related species.
An interesting new study (see item 1 in the ‘Missing Links’ section below) made use of Darwin’s realisation that species’ geographical distributions tend to reflect their genealogical descent. The study compared two different taxonomic techniques for classifying species: the traditional technique of comparing their morphologies, and the more recent technique of comparing their DNA. It found that DNA-based taxonomies more closely reflected species’ geographical groupings than did morphology-based taxonomies. In other words, DNA-based taxonomies tend to be more accurate than morphology-based taxonomies at reflecting genealogical descent.
When done properly, science has an admirable habit of spotting its own mistakes and correcting them. One implication of this new study, assuming its findings are widely accepted, is that many of our existing morphology-based taxonomies will require revision. Those where DNA comparisons can be made, at least. For those species where no DNA samples exist—which includes the vast majority of extinct species—more traditional morphology-based techniques remain the best approach we have.
Some Darwin- and evolution-related stories that caught my eye recently:
- Study suggests that most of our evolutionary trees could be wrong
Scientists compared evolutionary trees based on morphology with those based on molecular data, and mapped them according to geographical location. They found that the animals grouped together by molecular trees lived more closely together geographically than the animals grouped using the morphological trees.
Associated journal paper: Molecular phylogenies map to biogeography better than morphological ones
- Microfossils may be evidence life began ‘very quickly’ after Earth formed
Scientists believe a new specimen shows life existed earlier than is widely assumed.
- Pterosaurs and the evolution of melanin-based colours in feathers: pterosaurs had feathers and they were coloured!
A remarkably well-preserved Pterosaur fossil reveals clues that it bore coloured feathers.
- How the dinosaur extinction changed plant evolution
Following the extinction of non-avian dinosaurs 66 million years ago, large herbivores were missing on Earth for 25 million years. This raises the question of how the prolonged absence of ‘mega-herbivores’ affected the evolution of plants.
- Wild animals are evolving faster than anybody thought
A long-term study of wild animal populations shows each generation is on average almost 20% genetically ‘better’ than its parents at surviving and reproducing.
- Catastrophe drives evolution. But life resides in the pauses
Evolution is extraordinarily creative in the wake of a cataclysm. How does life keep steadily ticking over in between?
- Chimpanzees combine calls to form numerous vocal sequences
Evidence of structured vocal sequences in wild chimpanzee communication provides insights into human language evolution.
Associated journal paper: Chimpanzees produce diverse vocal sequences with ordered and recombinatorial properties
- Strange fossil solves giraffe evolutionary mystery
Fossils of a strange early giraffoid have revealed what is claimed to be the key driving forces in giraffe evolution.
- Largest ever study of its kind reveals whales evolved in three rapid phases
A new study has revealed that the diversity we see in whale skulls was achieved through three key periods of rapid evolution.
- ’Fantastic giant tortoise’ species thought extinct for 100 years found alive
A rare Galápagos species, the ‘fantastic giant tortoise‘, long thought extinct, has been officially identified for the first time in more than a century.
- The Platypus Conspiracy
Extremely silly video. (It’s Jerry’s fault.)
For regular links like these, please like and follow the Friends of Charles Darwin Facebook page.
Some book recommendations for you:
Journal of Researches
The first draft of my Darwin book continues to evolve at an appropriately slow but steady pace, occasionally punctuated by brief bursts of activity. I have now written 88,000 words of my target 65,000—which just goes to show how bad I am at setting targets.
My latest chapter was about something Darwin got very, very wrong: his ‘provisional hypothesis’ of Pangenesis, in which he attempted to explain how heredity works. You won’t be at all surprised to hear I cut poor old Charlie a bit of slack, concluding it wasn’t such a bad attempt, given the various phenomena he was trying to explain—at least one of which, while generally accepted at the time, we now know to be completely bogus.
Expression of Emotions
Thanks for taking time to read this newsletter. As always, please feel free to forward it to any friends you think might like to subscribe. If you enjoy this newsletter, you might also like to check out my other newsletter, which is remarkably similar in format, but with less emphasis on Darwin-related stuff.
See you next time!
Richard Carter, FCD