An international research team from Swansea University and UBC Okanagan has conducted a study comparing the hearts of humans with those of other great apes, seeking to gain insight into human evolution. Despite sharing a common ancestor, humans have evolved larger brains and the ability to walk upright, likely for hunting purposes. The team’s research, published in Communications Biology, found differences in the structure and function of the left ventricle of the heart between humans and non-human great apes.
The team compared the hearts of humans with those of chimpanzees, orangutans, gorillas, and bonobos in wildlife sanctuaries and zoos using echocardiography. They discovered that the left ventricle of non-human great apes had a more trabeculated, mesh-like network of muscle compared to the predominantly compact muscle in humans. This difference was most pronounced at the apex of the heart, with non-human great apes having approximately four times the trabeculation of humans.
By using speckle-tracking echocardiography, the team also measured the heart’s movement and velocities, finding that the degree of trabeculation was related to cardiac function. They observed that humans, who have the least trabeculation, exhibited greater cardiac function compared to non-human great apes. This supports the hypothesis that the human heart may have evolved differently to meet the higher demands imposed by humans’ unique ecological niche.
The team suggests that the larger brain and increased physical activity of humans compared to other great apes may be linked to a higher metabolic demand, requiring a heart capable of pumping a greater volume of blood. This increased blood flow also helps humans regulate body temperature by dissipating heat through dilated blood vessels close to the skin. The researchers believe that the human heart may have adapted to meet the demands of walking upright and managing thermal stress throughout evolution.
The study also raises questions about the adaptive significance of the more trabeculated hearts of non-human great apes in their ecological niches. It is unclear why these animals have a different heart structure compared to humans, but it may be a remnant of their ancestral heart structure. The researchers emphasize the importance of understanding how form and function are interlinked in evolution, with the human heart possibly evolving away from the structure of non-human great apes to meet the specific demands of human physiology.
The research team expresses gratitude to the staff and volunteers caring for the animals involved in the study at various wildlife sanctuaries and zoos. Their collaboration with organizations such as the Tchimpounga Wildlife Sanctuary, Chimfunshi Wildlife Sanctuary, and Zoological Society of London helped provide valuable insights into the evolutionary differences in heart structure among humans and non-human great apes. This study contributes to a better understanding of how human evolution has shaped our cardiovascular system in response to unique ecological challenges.