An international research team from Swansea University and UBC Okanagan (UBCO) has made a breakthrough in understanding human evolution by comparing human hearts to those of other great apes. Despite sharing a common ancestor, humans have evolved larger brains and the ability to walk or run upright on two feet for long distances, likely for hunting. This new study compares the structure and function of the hearts of humans and great apes.The function of the heart was the subject of a study published in Communications Biology, where researchers have made a new discovery in the evolutionary puzzle. The team conducted comparisons of the human heart with those of our closest evolutionary relatives, such as chimpanzees, orangutans, gorillas, and bonobos. These animals were cared for in wildlife sanctuaries in Africa and zoos across Europe. The team utilized echocardiography, a method of cardiac ultrasound, during routine veterinary procedures on the great apes to generate images of the left ventricle, the chamber responsible for pumping blood throughout the body. In the left ventricle of non-human great apes, bundles of The left ventricle of a healthy human has a relatively smooth surface with mostly compact muscle, while non-human great apes have a more trabeculated, mesh-like network. The difference is most noticeable at the bottom of the heart, with non-human great apes having about four times the amount of trabeculation compared to humans. The team also used speckle-tracking echocardiography to measure the heart’s movement and velocities. The study looked at the pattern of the cardiac muscle as it contracts and relaxes.
According to Bryony, they discovered a relationship between the degree of trabeculation in the heart and the amount of deformation, rotation, and twist. Specifically, humans with the least trabeculation showed greater cardiac function. This suggests that the structure of the human heart may have evolved differently from that of other non-human great apes to meet the higher demands of humans’ unique ecological niche.
Additionally, a human’s larger brain and greater physical activity compared to other great apes can also be connected to this finding. The shift to walking upright led to an increased need for energy, requiring the heart to be able to pump a larger volume of blood throughout the body. Additionally, the greater blood flow helps humans cool down by allowing blood vessels near the skin to expand and release heat to the air.
According to Dr. Aimee Drane, a Senior Lecturer at Swansea University, these findings may indicate that the human heart faced selective pressure in evolution to adjust to the demands of walking upright and regulating body temperature. However, it is still uncertain how the more trabeculated The hearts of non-human great apes are well-suited to their own habitats, suggesting that they may have evolved to meet the specific needs of their ecological niches. This could be a remnant of their ancestral heart structure, as in nature, the form of an organ is often closely related to its function.”
The research team would like to express their gratitude to the staff and volunteers who provide care for the animals involved in the study. This includes the teams at 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).
