Scientists have long thought that a human’s first heartbeat takes place on the 21st day after conception, but new research from the University of Oxford shows that it could be even earlier, at just 16 days after conception.

The findings were published this week in the journal eLife as a clinical study that looked at mouse embryos and extrapolated heart development patterns to humans. The study was led by Paul Riley, a professor at the British Heart Foundation, the organization that funded the majority of the study.

Riley and his team found that in mice, the cardiac crescent forms 7.5 days after conception, which is about equivalent to 16 days in a human embryo. They were able to tell at which point in time calcium cells made the heart muscle cells contract using fluorescent markers.

“We hope that this new research will help us learn how the beating of new heart muscle cells might be triggered in replaced muscle after a heart attack,” Riley said in a statement from the college.

These findings can better help physicians identify problems in a fetus’ heart, potentially avoiding the development of congenital heart disease. Additionally, greater understanding of how the heart develops could help cardiologists better repair damaged muscle tissue in a patient who has experienced a heart attack.

“By finding out how the heart first starts to beat and how problems can arise in heart development, we are one step closer to being able to prevent heart conditions from arising during pregnancy,” Riley said.

The study was also partly funded by the Wellcome Trust and the Biotechnology and Biological Sciences Research Council.