Logic and evolution: the giraffe problem (Introduction)

by David Turell , Wednesday, March 17, 2021, 21:57 (1345 days ago) @ David Turell

There is n o evidence for a gradual elongation of the giraffe neck. In the fossil record it just appears:

http://www.weloennig.de/Giraffe.pdf

"This new study attempts to explain the massive physiological changes required by the very long neck:

https://phys.org/news/2021-03-tall-giraffes-genes.html

"The extraordinary stature of the giraffe has led to a long list of physiological co-adaptations. The blood pressure of the giraffe, for instance, is twice as high as in humans and most other mammals to allow a steady blood supply to the lofty head. How does the giraffe avoid the usual side effects of high blood pressure, such as severe damage to the cardiovascular system or strokes?

"The team discovered a particular gene—known as FGFRL1—that has undergone many changes in the giraffe compared to all other animals. Using sophisticated gene editing techniques they introduced giraffe-specific FGFRL1 mutations into lab mice. Interestingly, the giraffe-type mice differed from normal mice in two important aspects: they suffered less cardiovascular and organ damage when treated with a blood pressure increasing drug, and they grew more compact and denser bones.

"'Both of these changes are directly related to the unique physiological features of the giraffe—coping with high blood pressure and maintaining compact and strong bones, despite growing them faster than any other mammal, to form the elongated neck and legs," says Rasmus Heller from the Department of Biology, University of Copenhagen,...

"While jumping out of bed for (some) humans might be an effortless and elegant affair, this is definitely not the case for the giraffe. Merely standing up is an a lengthy and awkward procedure, let alone getting up and running away from a ferocious predator. Therefore, giraffes have evolved into spending much less time sleeping than most other mammals.

"Rasmus Heller elaborates: "We found that key genes regulating the circadian rhythm and sleep were under strong selection in giraffes, possibly allowing the giraffe a more interrupted sleep-wake cycle than other mammals."

In line with research in other animals an evolutionary trade-off also seem to be determining their sensory perception, Rasmus continues, "Giraffes are in general very alert and exploit their height advantage to scan the horizon using their excellent eyesight. Conversely, they have lost many genes related to olfaction, which is probably related to a radically diluted presence of scents at 5m compared to ground level."

"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."

Comment: The bold above describes the problem perfectly. How so many complex physiological changes so coordinated appear so quickly? Of course, the authors think a Darwin style gene did the job all by itself like an octopus with all its arms in action. How did a naturally occurring chance set of mutations find the perfect gene? It is much easier for me to propose the designer did it.