Human hearts evolved for endurance due to shift from hunting to farming and a modern lifestyle

Hearts evolved to make humans better at endurance tasks, a new study has found.

According to research conducted by scientists from Canada, the U.K. and the U.S., this change — which started around the time people shifted from being hunter-gatherers to being farmers — enabled humans to become more efficient at maintaining their energy levels over longer periods of time.

This, the researchers said, is what differentiates human hearts from those of apes, which are considered the closest genetic relatives of humans.

According to Robert Shave, a cardiovascular physiologist at the University of British Columbia Okanagan, while apes such as gorillas and chimpanzees tend to spend a lot of time sleeping or being relatively inactive, they are prone to exhibiting short bursts of physical activity.

“With chimpanzees, it’s very quiet and calm, and then you have high bursts of very, very intense physical activity,” Shave said, noting that this puts intense pressure on the chimps’ hearts, albeit for short amounts of time. (Related: Is your lifestyle leading to a heart attack? Learn how to protect yourself with “Prevent and Reverse Heart Disease”.)

This is in stark contrast to humans, who are active for longer periods of time in order to hunt and farm.

These differences in lifestyles, according to lead researcher Aaron Baggish, led to physical changes in the hearts themselves.

“Humans have longer, thinner- and more flexible-walled hearts, while chimps have smaller hearts with thicker walls,” Baggish said.

Aside from the difference in the thickness of their hearts’ walls, one other significant difference between the hearts of humans and apes is that when human hearts pump, they also rotate.

According to the researchers, this twisting motion helps the heart push more blood out each time it beats and draw more blood in when it pumps.

“It’s something new that came in with humans,” Shave said, adding that the motion is not present in the hearts of either chimpanzees or gorillas.

Sedentary individuals have “ape-like” hearts

For their study, which was published in the journal PNAS, the researchers carried out detailed heart function studies on around 160 study participants. They divided the human participants into four groups — endurance athletes, American football players, indigenous Mexican farmers and sedentary individuals — based on their level of physical activity.

The researchers then conducted the same tests on 40 semi-wild chimpanzees and five gorillas.

“The goal was to compare heart structure and function in each ‘type’ – whether the subject was very active, to barely active,” Baggish said.

The researchers found that human hearts “transformed” over time to handle certain activities that require endurance, in contrast to shorter but more taxing activities.

Endurance athletes and football players, for instance, have longer, larger and more elastic left ventricles — one of the four chambers of the heart. According to the researchers, this trait made it easier to pump blood throughout the body for an extended period of time.

Those who led sedentary lives, on the other hand, had hearts that were more “ape-like” in that they seemed to be more suited for short but intense bursts of physical activity.

In addition to the “ape-like” traits, the sedentary individuals who participated in the tests were also found to be highly prone to hypertension – a known risk factor for cardiovascular disease.

According to the researchers, not only do their findings help answer important questions about the heart’s evolution, but their study also has important implications for understanding heart health and heart disease. They noted that their findings challenge the established understanding of how high blood pressure begins, how the heart reacts and how heart disease develops.

For similar stories about the heart as well as tips on how to maintain optimal heart health, visit Heart.News.

Sources include:

DailyMail.co.uk

PNAS.org

Eurekalert.org

InsideScience.org

HMS.Harvard.edu

Earth.com