Evolutionary Rates Vary by Millions

When an organism changes rapidly, that’s evolution. When an
organism never changes for millions of years, that’s evolution.

Evolution is as evolution does. When a plant or animal adapts within a single generation, that qualifies as an example of Darwinian evolution, its adherents claim. When an organism never changes for hundreds of millions of years, that’s Darwinian evolution, too. The rate of evolution covers 8 orders of magnitude. In length, 8 orders of magnitude like the difference between a centimeter and 1,000 kilometers, or the width of your little fingernail and the distance from New York City to Nashville, Tennessee. In travel speed, it’s like the difference between half an inch per hour and the land speed record for a car, 760 mph.

The following articles show that the alleged “rate of evolution” varies all over the map, from rapid to a near standstill. Fruit flies can adapt within a generation or two within a year, but horseshoe crabs (another kind of arthropod in the same phylum) have barely changed for hundreds of millions of years.

How predictable is rapid evolution? (Behrman and Schmidt, bioRxiv, 28 Oct 2022). Forget the millions of years. Fruit flies can evolve within a year, these two say. In no time these flies should be able to evolve large brains that can do Drosophilosophy.

Although evolution is historically considered a slow, gradual process, it is now clear that evolution can occur rapidly over generational timescales. It remains unclear both how predictable rapid evolution is and what timescales are ecologically relevant due to a paucity of longitudinal studies. We use a common garden approach to measure genetic-based change in complex, fitness-associated traits that are important for climatic adaptation in wild Drosophila over multiple timescales: an estimated 1-16 generations within each year and 48-89 generations over five consecutive years. Evolution is fast and pervasive with parallel patterns of rapid evolution in three distinct locations that span 4 degrees latitude. Developmental time evolves consistently across seasons with flies collected in spring developing faster than those collected in autumn.

Ancestral genetic variation essential for rapid evolution of Darwin’s finches (Uppsala University, 11 July 2022). Yes, Darwin’s finches, those icons of evolution, can evolve rapidly, reaching into their bag of ancestral genes.

An important question in evolutionary biology is how such rapid evolution can take place?

Darwin’s finches have evolved in a relatively undisturbed environment: the archipelago is located about 1,500 kilometers west of mainland South America. Permanent human settlements have only existed within the last 100 years, and no species of Darwin’s finches has become extinct due to human activities.

Transplant experiments demonstrate that larger brains are favoured in high-competition environments in Trinidadian killifish (Ecology Letters, 19 Oct 2022). A species of fish adapted to a new environment within the experimental observation time.

The extent to which the evolution of a larger brain is adaptive remains controversial. Trinidadian killifish (Anablepsoides hartii) are found in sites that differ in predation intensity; fish that experience decreased predation and increased intraspecific competition exhibit larger brains. We evaluated the connection between brain size and fitness (survival and growth) when killifish are found in their native habitats and when fish are transplanted from sites with predators to high-competition sites that lack predators. Selection for a larger brain was absent within locally adapted populations. Conversely, there was a strong positive relationship between brain size and growth in transplanted but not resident fish in high-competition environments. We also observed significantly larger brain sizes in the transplanted fish that were recaptured at the end of the experiment versus those that were not.

Brain evolution is linked to competition (University of Texas at Arlington, 20 Oct 2022). This press release about the above paper says that competition causes the evolution of bigger brains, but didn’t mention that it happened rapidly.

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today (McMaster University, 19 Oct 2022). Within a few centuries after the medieval plague, these scientists claim to see that human immune genes evolved. That’s just in a few hundred years. Wouldn’t humans have perfect immune systems after a thousand times more time than that?

“The selective advantage associated with the selected loci are among the strongest ever reported in humans showing how a single pathogen can have such a strong impact to the evolution of the immune system,” says human geneticist Luis Barreiro, an author on the paper, and professor in Genetic Medicine at the University of Chicago.

The team reports that over time our immune systems have evolved to respond in different ways to pathogens, to the point that what had once been a protective gene against plague in the Middle Ages is today associated with increased susceptibility to autoimmune diseases. This is the balancing act upon which evolution plays with our genome.

Weird and wonderful world of fungi shaped by evolutionary bursts, study finds (University of Bristol, 17 Aug 2022). Behold, evolution can burst forth like fireworks, only to remain stable for millions of years. How does that happen? Because evolution is driven by evolution, that’s how.

What they found was that fungal disparity has evolved episodically through time, and that the evolution of multicellularity in different fungi appears to open the door for greater morphological variety. They saw increases in disparity associated with both the emergence of the first multicellular fungi, and then the evolution of complex fruiting bodies such as mushrooms….

Mr Smith said: “The world of fungi is defined by bright colours, strange shapes, and stranger anatomies. Our analyses demonstrate that this breath-taking anatomical variety has evolved in bursts, driven by evolutionary increases in multicellular complexity.”

Molecular early burst associated with the diversification of birds at the K–Pg boundary (Berv et al., bioRxiv, 22 Oct 2022). Like fireworks? Enjoy the bird burst! Learn about “a burst of genomic disparity early in the evolutionary history of crown [evolved, derived] birds.” See the whole fireworks show across the entire tree of life in this video.

Imaginary bird evolving into a penguin. Can’t fly or swim. Will it survive until the next lucky mutations?

Over 60 million years ago, penguins abandoned flight for swimming. Here’s how. (Live Science, 29 July 2022). Long, long ago, Stephanie Pappas tells the readers of her just-so story, penguins dropped out of the sky and began swimming. And they’ve remained penguins ever since. “It doesn’t affect all species equally, but it’s almost like someone is turning a crank to make more penguin species,” said one of her preferred Darwinist experts.

Evolving to outpace climate change, tiny marine animal provides new evidence of long-theorized genetic mechanism (University of Wisconsin-Madison, 14 July 2022). Why worry? Organisms can evolve faster than climate change, says this press release. Little copepods in the ocean are using “positive epistasis” to outrun warming. Isn’t evolution wonderful? Like fire to Prometheus, the Stuff Happens Law brings mankind that coveted gift: understanding.

“This copepod gives us an idea of what it takes, an idea of what the conditions are needed, that enable a population to evolve rapidly in response to climate change,” says Lee. “It also shows how important evolution is for understanding our changing planet and how — or even whether — populations and ecosystems will survive.”

Monkeypox may have undergone ‘accelerated evolution,’ scientists say (Live Science, 25 June 2022). Did you know the DarwinMobile comes with an accelerator pedal that kicks in the hyperdrive?

The monkeypox virus has mutated at a far faster rate than would normally be expected and likely underwent a period of ‘accelerated evolution,’ a new study suggests.

Genetic variance in fitness indicates rapid contemporary adaptive evolution in wild animals (Science Magazine, 26 May 2022). “Rapid Change” reads the first subtitle of this report. “Bonnet et al. looked at additive genetic variance, which determines the contribution of selection to genetic change that increases fitness, in long-term data from 19 species and found it to be higher than expected—often substantially higher,” reads the opening paragraph.

Wild animals are evolving faster than anybody thought (The Conversation, 26 May 2022). Bonnet, lead author of the above paper, is amazed at how fast evolution can take place. But did everybody think that? He said “faster than anybody thought.”

How fast is evolution? In adaptive evolution, natural selection causes genetic changes in traits that favour the survival and reproduction of individual organisms.

Although Charles Darwin thought the process occurred over geological timescales, we have seen examples of dramatic adaptive evolution over only a handful of generations.

Wild animals evolving much faster than previously thought (Australian National University, 27 May 2022). Dr Bonnet’s school wants some of the credit for this revelation about fast-track evolution. Bonnet says, “evolution is a much more significant driver than we previously thought in the adaptability of populations to current environmental changes.” But is evolution both driver and passenger?

According to Dr Bonnet, the process of evolution that Darwin described was an incredibly slow one.

“However, since Darwin, researchers have identified many examples of Darwinian evolution occurring in just a few years,” Dr Bonnet said.

My, what would Darwin think? He would be pleased as long as his name is still attached to “the process” by which stuff happens: Darwinian evolution.

Now read our 11 Oct 2022 entry living fossils – organisms that stay the same for up to hundreds of millions of years. A related entry about things evolving “earlier than thought” was posted on 20 Oct 2022.

So there you have it: evolution drives evolution as fast or slow as needed to keep the Darwin Storytelling Empire in business! Now you have… underssssstandinggggg.

Cartoon for CEH by Brett Miller. All rights reserved.