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Giraffe Genome Is Not Evolutionary

Photo credit: Elizabeth Smith, via Unsplash.

What biology student has not been tested on Lamarck vs. Darwin’s explanations for the giraffe? It’s one of the obligatory stories on evolution in textbooks. Lamarck thought that the necks became longer as giraffes stretched for the treetops and their offspring inherited those acquired characteristics. Students hear about problems with that view (usually with auxiliary stories about Weismann’s experiments chopping off the tails of generations of mice). Then, Darwin’s mechanism — natural selection — is introduced as the victor. Congratulations usually follow about Darwin being one of the most original thinkers in the history of science. (What students are not told is that Darwin became more Lamarckian in later revisions of the Origin due to increasing criticisms of natural selection.)

But what if both views are misguided? What if the real explanation is not evolutionary? Lamarck and Darwin both assumed that the giraffe evolved from some pre-giraffe with a short neck. Is that assumption necessary? It only seems necessary if one starts with the assumption of universal common ancestry by unguided natural processes. A few outliers, like structuralists or theistic evolutionists, might quibble with that claim, but the majority of evolutionary biologists do not tolerate any guidance or direction to the evolutionary process (hear J. P. Moreland explain this on ID the Future). The giraffe body plan, with all its unique traits, was never a goal in Darwinism or Lamarckism. Things just turned out that way.

The Gene of the Giraffe

A new complete giraffe genome is beginning to shed light on which view has more empirical support. Published by Chang Liu et al. in Science Advances (open access), it gives biologists a fresh start in discerning links between genotype and phenotype for this unique iconic animal. 

The suite of adaptations associated with the extreme stature of the giraffe has long interested biologists and physiologists. By generating a high-quality chromosome-level giraffe genome and a comprehensive comparison with other ruminant genomes, we identified a robust catalog of giraffe-specific mutations. These are primarily related to cardiovascular, bone growth, vision, hearing, and circadian functions. [Emphasis added.]

Most summaries of the paper, including those in Science magazine and The Scientist, fail to account for the long neck — the very trait that most interested the early evolutionists. Instead, they focus on one particular gene named FGFRL1. In humans and mice, this gene is associated with bone strength and with blood pressure. 

The team decided to check what happens when the giraffe version of the gene, with has seven differences from the gene in other mammals, is inserted into mouse embryos. The mice did not grow long necks, but they grew more compact and denser bones. Most importantly, they also survived a drug that raises blood pressure. Giraffe blood pressure is twice that of humans. It appears, therefore, that giraffes have a version of FGFRL1 that protects them from the expected damage to tissues and organs from blood pressure high enough to pump blood up to their lofty 5-meter-high heads. Why is this gene also associated with bone growth? 

These findings provide insights into basic modes of evolution. The dual effects of the strongly selected FGFRL1 gene are compatible with the phenomenon that one gene can affect several different aspects of the phenotype, so called evolutionary pleiotropy. Pleiotropy is particularly relevant for explaining unusually large phenotypic changes, because such changes often require that a suite of traits are changed within a short evolutionary time. Therefore, pleiotropy could provide one solution to the riddle of how evolution could achieve the many co-dependent changes needed to form an animal as extreme as a giraffe.

A few other interesting things were found in the genome: genes related to circadian rhythms that might explain why giraffes get by with little sleep (since getting up off the ground is a “lengthy and awkward procedure”), why their olfactory genes are reduced (“probably related to a radically diluted presence of scents at 5m compared to ground level”), and why their eyesight is so sharp (assumed to be an evolutionary trade-off for less reliance on the sense of smell). The most obvious traits of the giraffe — the long neck, long legs, fur patterns and all — have not been addressed in the paper. The authors admit that “more research on the functional consequences of giraffe-specific genetic variants is needed.”

Lucky Pleiotropy

If pleiotropy is the explanation for the giraffe, what a lucky mutation in FGFRL1 must have occurred! Not only did it protect the giraffe from high blood pressure, it simultaneously switched on some other gene that created denser, faster-growing bones that the giraffe needs to reach its full height without breaking its neck in the process. The authors conclude:

Overall, these results show that pleiotropy is a plausible mechanism for contributing to the suite of co-adaptations necessary in the evolution of the giraffe’s towering stature.

Since pleiotropy sounds like a good explanation for that, why not invoke it all over the animal? Think how it would reduce the number of lucky mutations. Evolution could get more done in less time by winning the red powerball. One mutation might create the fur patterns, put in the spongy brain that prevents a hemorrhage when the giraffe stoops to drink, rearrange the blood vessels and nerves, and do a dozen other things that otherwise would require separate chance mutations. Obviously, that gets silly. If the giraffe evolved to its current status gradually, it would have to win multiple red powerballs to keep its traits in sync as they change. 

The Bad “Evolutionary” Habit

Throughout these articles, one can see the writers inserting the adjective “evolutionary” in front of everything. 

  • “an evolutionary geneticist at the University of Copenhagen” — why not just a geneticist?
  • “giraffes are a poster child for evolutionary oddities” — why not just oddities?
  • “several phenotypic traits that share evolutionary constraints” — why not just constraints, as in engineering specifications?
  • “This [reduction in olfactory sensitivity] may be an evolutionary consequence of enhanced vision” — why not just a consequence, as in a designed trade-off for multiple competing specifications?
  • “evolutionary adaptations” — why not just adaptations, or unique traits fit for the giraffe’s ecological niche?
  • “evolutionary pleiotropy” — why not just pleiotropy?
  • “a suite of traits are changed within a short evolutionary time” — why not a suite of traits that work together?

Typists could avoid carpal tunnel syndrome by eliminating this unnecessary word in science papers and news stories. It seems that the “evolutionary” biologists, who should just call themselves biologists, want to push a narrative that everything in the living world must pay tribute to Darwin. The repetition of the word hammers it into people’s heads. Everything in nature, they are taught with this propaganda tactic, is part of a fluid phantasmagoric tableau where every creature came from some other creature and is becoming something else. 

In fact, what’s important is understanding the design of the giraffe: how its genes produce the traits, and how the traits make it successful in its environment. That much should be sufficient for scientific understanding. The “evolutionary” narrative reflects a philosophical predilection. Since one’s worldview preference is unrelated to the empirical content of scientific research, it should be stated up front for full disclosure. Wouldn’t that make readers more astute!