Saturday, 20 March 2021

Evolution News - How to Make a Giraffe Without Using Magic

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Photo credit: Mogens Trolle
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Reticulated Giraffe, Buffalo Springs, Kenya.
Photo credit: Mogens Trolle
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Help Us Stand Tall for Giraffes.
The U.S. is one of the leading importers of giraffe parts. We need your help persuading America’s leaders to protect them before they’re gone.

Photo by Philippe Chantecaille
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"The Last Giraffes on Earth"
Source: The Atlantic
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Image credit: San Diego Zoo
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Giraffes, found throughout sub-Saharan Africa, are susceptible to poaching and habitat loss.

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Giraffes on the Masai Mara National Reserve in Kenya.
Credit: Goran Tomasevic/Reuters
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Reticulated sub-species of Giraffe at Loisaba conservancy in Laikipia, Kenya. As across the rest of African, they have declined steadily in recent decades.
Credit: AFP/Tony Karumba
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Girafffes in the Masai Mara.
Credit: Manoj Shah/Getty
Source: BBC Wildlife
The Trouble of Being Tall – Biologisk Institut - Københavns Universitet

Researchers at the Biologisk Institut, University of Copenhagen, and Northwestern Polytechnical University in China have succeeded in sequencing the whole genome of the giraffe and in doing so have uncovered the mechanisms by which giraffes evolved their unique features.

Evolving a long neck and tall stature presented the giraffe with a number of physiological and anatomical challenges:
  • A very high blood pressure is needed to pump blood up to the brain. The giraffe BP is about twice the normal BP for a mammal and would normally cause severe damage to the cardiovascular system.
  • Standing up from a lying position is difficult, as is bending down to drink, making the giraffe especially vulnerable while sleeping and drinking.
  • At about 5 metres above the ground, there is little role for a sense of smell.
The researchers found a number of evolved genetic features which help giraffes overcome these problems, including a version of the FGFRL1 with seven amino acid substitutions compared with the same gene in other ruminants. When tested in mice, this gene gave them added protection against damage from high blood pressure and more compact, denser bones. The team believe the function of this gene may have application in the treatment of high blood pressure in humans.

As the Biologisk Institut news release explains:
The giraffe is a truly puzzling animal. With its exceptional anatomy and suite of evolutionary adaptations, the giraffe is an outstanding case of animal evolution and physiology. Now, an international team of researchers from the University of Copenhagen and Northwestern Polytechnical University in China have produced a high-quality genome from the giraffe and investigated which genes are likely to be responsible for its unique biological features.

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?

Photo credit: Mogens Trolle

Testing giraffe mutations/genes in mice


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.

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.

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.

Rasmus Heller, joint lead author
Department of Biology
University of Copenhagen
- “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, one of the lead authors on the study.

Giraffe’s can’t get no sleep


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:

Photo credit: Mogens Trolle
- “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”.

A model of evolutionary mechanisms—and perhaps even human medicine?


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.
These results showcase that animals are interesting models, not only to understand the basic principles of evolution, but also to help us understand which genes influence some of the phenotypes we are really interested in – such as those related to disease. However, it’s worth pointing out that genetic variants do not necessarily have the same phenotypic effect in different species, and that phenotypes are affected by many other things than variation in coding regions.

Qiang Qiu, Joint lead author
School of Ecology and Environment
Northwestern Polytechnical University
Xi’an, China.
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. Furthermore, the findings even identifies FGFRL1 as a possible target of research in human cardiovascular disease.

- “These results showcase that animals are interesting models, not only to understand the basic principles of evolution, but also to help us understand which genes influence some of the phenotypes we are really interested in – such as those related to disease. However, it’s worth pointing out that genetic variants do not necessarily have the same phenotypic effect in different species, and that phenotypes are affected by many other things than variation in coding regions.”, says Qiang Qiu from Northwestern Polytechnical University, another lead author on the study.
The results have just been published open access in Science Advances.

Abstract


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. Among them, the giraffe FGFRL1 gene is an outlier with seven unique amino acid substitutions not found in any other ruminant. Gene-edited mice with the giraffe-type FGFRL1 show exceptional hypertension resistance and higher bone mineral density, both of which are tightly connected with giraffe adaptations to high stature. Our results facilitate a deeper understanding of the molecular mechanism underpinning distinct giraffe traits, and may provide insights into the study of hypertension in humans.

Would any creationist like to dispute the patently obvious fact that the seven mutations in the giraffe's FGFRL1 gene were beneficial, not deleterious as Creationist dogma now insists? How exactly can these mutations be presented as 'devolutionary' (© 2019 Michael J Behe/Discovery Institute)? In what way would a giraffe with damage to its cardiovascular system from high blood pressure, and weak bones, be more perfect than the ones which carry this mutation? In other words, how are these mutations devolutionary from the initial perfection at the supposed spontaneous magic creation of giraffes?






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