A study comparing human and great ape hearts revealed key evolutionary adaptations in humans, including smoother heart muscle with fewer trabeculae that improves heart function to support higher metabolic demands and efficient thermoregulation.
An international team of researchers from Swansea University and UBC Okanagan has gained new insights into human evolution by studying the hearts of humans and other great apes. Despite a common ancestry, humans developed larger brains and the ability to walk or run on two legs; adaptations likely developed for long-distance travel and hunting.
Now, thanks to a new comparative study of heart shape and function, Biology of Communication The researchers believe they have discovered another piece of the evolutionary puzzle. The team compared the human heart with the hearts of our closest evolutionary relatives, including chimpanzees, orangutans, gorillas and bonobos kept in wildlife reserves in Africa and zoos in Europe.
Methodology and results of the heart comparison
During routine veterinary procedures on these great apes, the team used echocardiography (an ultrasound of the heart) to take images of the heart’s left ventricle, the chamber that pumps blood around the body. In a great ape’s left ventricle, bundles of muscle extend into a chamber called a trabeculation.
Bryony Currie, a graduate student in the School of Health and Exercise Sciences at UBCO, said: “The healthy human left ventricle is relatively smooth with mostly compact muscles, compared to the more trabeculated, reticular network in non-human great apes.
“The difference is most pronounced at the apex, the lower part of the heart, where we found that trabeculation is four times greater in great apes than in humans.”
Advanced Imaging Techniques and Their Evolutionary Impacts
The team also measured heart movement and rate using speckle-tracking echocardiography, an imaging technique that tracks the structure of the heart muscle as it contracts and relaxes.
“We found that the degree of trabeculation in the heart correlates with the degree of deformation, rotation and twisting. That is, we observed relatively greater heart function in individuals with the least trabeculation. This discovery supports our hypothesis that the human heart may have evolved from the structure of other great apes to meet the higher demands of humans’ unique ecological environment,” Briony said.
The larger brains and greater physical activity of humans compared to other great apes may also be related to higher metabolic demands, requiring a heart that can pump greater amounts of blood throughout the body. Similarly, increased blood flow contributes to a person’s ability to cool down, due to the dilation of blood vessels near the skin (seen as reddening of the skin) and the loss of heat to the air.
Dr Amy Drain, senior lecturer in the School of Medicine, Health and Life Sciences at Swansea University, said: “From an evolutionary perspective, our findings may suggest that the human heart has selective pressure to adapt to the demands of upright walking and to manage thermal stress.
“What remains unclear is how the trabeculated hearts of great apes may have adapted to their particular ecological niche. Perhaps this is an ancestral heart structure, but in nature this form mostly serves a specific function.”
Source: Port Altele
