Giraffes and Genomes

Can we all, for a moment, stop what we’re doing and appreciate giraffes?

To appreciate giraffes, of course, means to appreciate their anatomy. Their black-tipped tongues measure up to 20 inches. A joint, at the base of their skull, allows them to lift their head in line with the neck as they angle for leaves. At six feet, giraffes’ necks alone are probably taller than the person reading this. Spread out over those six feet are seven vertebrae – the same amount as humans – whose ball-and-socket connections allow the animals to rub their nose to their lower back.

Arteries in the legs are narrow, while arteries above the heart are wide and beefy, to enable the heart in its gravity-defying act of pumping blood to the brain. Giraffes’ anatomical oddities go on and on, but you get the point: they are special creatures.

Their anatomical weirdness also offers scientists like Qiang Qiu, of Northwestern Polytechnical University in China, a window into how evolution works. Qiu, along with a team of researchers from the University of Copenhagen, generated a giraffe genome in March 2021. When they compared the genome with other animals, the scientists were able to distinguish specific genes that drove the evolutionary adaptations that make giraffes so unique.

Evolution is a game of trade-offs: an advantage in one area could mean a disadvantage in another. Giraffes are a prime example of this. Long necks and superior height translate to enhanced food access and a prime vantage point for detecting predators in the distance. Yet the perk comes with a price for the cardiovascular system, with a heart weighing 24 pounds and a blood pressure rate at two times the amount as most mammals. Scientists observing the genome also noticed that giraffes have “lost many genes related to olfaction, which is probably related to a radically diluted presence of scents at 5m compared to ground level.”

Long and compact legs turn getting up from a nap into an awkward, lengthy affair. Perhaps due to this evolutionary advantage/disadvantage, sleep duration in giraffes is among the lowest recorded in mammals. To this point, scientists studying the genome found “rapid acceleration” in PER1 and HCRT, genes that play a role in the regulation of sleep and arousal.

Understanding the genes that drive evolutionary adaptations in giraffes could lead to developments in the medical field. Scientists noticed another gene, FGFRL1, that progressed through several mutations in giraffes. Using advanced gene editing, Qiu and the team injected “giraffe-specific” FGFRL1 into lab mice. The team then tested FGFRL1 mice and normal mice with a drug to increase blood pressure. Two things happened: the edited mice suffered less cardiovascular damage and grew “more compact and denser bones.”

A mouse-giraffe hybrid is indeed a frightening prospect. But is it possible, at some point in the future, to treat hypertension in humans with a giraffe gene? Qiu and his team acknowledged a more thorough investigation is needed to understand the cardiovascular mechanisms of FGFRL1, but admit their findings “hold promise.”

Giraffes’ extreme anatomy reflects that evolution is more than just a zero-sum game or a linear progression of improvements in humans and animals. Even being an evolutionary wonder and the largest terrestrial mammal has its downfalls. Adaptations spur more adaptations, whether “good” or “bad.” Evolution just wants to keep evolving.

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