Research into the architecture of the heart offers new insight into human evolution

An international research team from Swansea University and UBC Okanagan (UBCO) has uncovered a new insight into human evolution by comparing the hearts of humans with those of other great apes.

Despite humans and non-human great apes having a common ancestor, the former evolved larger brains and the ability to walk or run upright on two feet to cover long distances, probably for hunting.

Now, through a new comparative study of the shape and function of the heart, published in Communication Biologyresearchers believe they have discovered a new piece of the evolutionary puzzle.

The team compared the human heart with those of our closest evolutionary relatives, including chimpanzees, orangutans, gorillas and bonobos cared for in nature reserves in Africa and zoos across Europe.

During routine veterinary procedures on these great apes, the team used echocardiography (a cardiac ultrasound) to create images of the left ventricle, the chamber of the heart that pumps blood around the body. In the left ventricle of the non-human great ape, muscle bundles extend into the ventricle, called trabeculations.

Bryony Curry, a Ph.D. student in UBCO’s School of Health and Exercise Sciences, said: “The left ventricle of a healthy human is relatively smooth, with predominantly compact muscles compared to the more trabeculous, mesh-like network in the non-human great apes.

“The difference is most pronounced at the apex, bottom of the heart, where we found about four times as much trabeculation in non-human apes as in humans.”

The team also measured the heart’s movement and speeds using speckle-tracking echocardiography, an imaging technique that follows the pattern of the heart muscle as it contracts and relaxes.

Curry said: “We found that the degree of trabeculation in the heart was related to the amount of deformation, rotation and twisting. In other words, in humans, who have the least trabeculation, we observed relatively greater cardiac function. This finding supports our hypothesis that the human heart may have evolved outside the structure of other non-human great apes to meet the higher demands of humans’ unique ecological niche.”

A human’s larger brain and greater physical activity compared to other great apes may also be associated with a higher metabolic demand, which requires a heart that can pump a greater volume of blood to the body.

Likewise, higher blood flow contributes to humans’ ability to cool down because the blood vessels close to the skin dilate – perceived as flushing of the skin – and lose heat to the air.

Dr. Aimee Drane, senior lecturer at Swansea University’s Faculty of Medicine, Health and Life Sciences, said: “In evolutionary terms, our findings may suggest that selective pressure was placed on the human heart to adapt to the demands of upright walking and move. managing thermal stress.

“What remains unclear is how the more trabeculated hearts of non-human great apes might adapt to their own ecological niches. Perhaps it is a remnant structure of the ancestral heart, although in nature form usually serves a function.”

The research team is grateful to the staff and volunteers who care for the animals in the study, including the teams from Tchimpounga Wildlife Sanctuary (Congo), Chimfunshi Wildlife Sanctuary (Zambia), Tacugama Chimpanzee Sanctuary (Sierra Leone), Nyaru Menteng Orangutan Rescue and Rehabilitation Center (Borneo), the Zoological Society of London (UK), Paignton Zoo (UK), Bristol Zoo Gardens (UK), Burgers’ Zoo (Netherlands) and Wilhelma Zoo (Germany).