Unlocking the mystery of what makes us human

Truly groundbreaking advances in science are sadly rare occurrences. So when they happen, we should celebrate them. The announcement that scientists have successfully created synthetic embryos from stem cells is one such advance.

The breakthrough was announced earlier this month in a plenary address at the annual meeting of the International Society for Stem Cell Research in Boston. Professor Magdalena Zernicka-Goetz, from Cambridge University, stated that it is now possible to create ‘human embryo-like models’ by reprogramming embryonic stem cells. These synthetic embryos avoid the need for eggs or sperm.

This breakthrough builds on work done last year by Zernicka-Goetz’s team and a rival group at the Weizmann Institute in Israel. Both groups developed stem cells from mice that self-assembled into early embryo-like structures. In April this year, researchers in China were also able to create synthetic embryos from monkey cells.

The development of ‘human embryo-like models’ is a huge advance on the development of earlier embryo-like structures. Although they are not actually human embryos, they will still deepen our understanding of human biology. More importantly, it will allow us to gain critical insights into a window of early human development that, until now, has remained primarily a ‘black box’. (This is partly due to the widely accepted 14-day rule, which requires that human embryos not be kept alive in vitro (longer than two weeks after fertilization or the developmental stage equivalent to when the embryos complete implantation.)

These models unlock this ‘black box’. They are developed from a single embryonic stem cell to reach the early stage of gastrulation – the developmental milestone that sets up the main axes of the body. No beating heart, no intestines, or even the beginnings of a brain. But remarkably, these model embryos show primordial cells, the precursors of egg and sperm cells – the source of life. Unsurprisingly, Zernicka-Goetz described this development as ‘beautiful’.

This certainly opens up an incredibly rich avenue of research that will be invaluable for people affected by infertility or genetic conditions. It promises to advance our understanding of human development, disease and reproduction. It will also improve established reproductive technologies, while opening up new possibilities of drug testing and development. Make no mistake, synthetic embryos can affect and improve the lives of millions of people.

At this point, these human embryo-like models have a very low chance of becoming living beings. It’s definitely not about ‘lab-grown babies’. However, Cambridge University has already launched a Governance of Stem Cell-Based Embryo Models (G-SCBEM) project, led by Cambridge Reproduction in partnership with the fertility charity, Progress Educational Trust (PET). The goal is to develop a control framework for this research.

These embryos are still required to raise ethical and philosophical questions. For a start, what, in a philosophical sense, is these ‘human embryo-like models’? Professor Zernicka-Goetz argues that, although they may look like embryos, complete with a three-dimensional structure, ‘they are not embryos’. Sandy Starr, deputy director of PET, said that while that question cannot be answered at this point, ‘which life form applies to reproductive materials is a very rich area for debate’.

Indeed, the research has sparked controversy, with scientists and ethicists debating how we should treat these not-quite-human embryos. For example, should they be subject to the same regulations as human embryos, complete with the 14-day rule? These questions touch on the biggest question of all – namely, what exactly makes us human?

The development of these synthetic embryos and the questions they raise should be welcomed. The history of science and medicine has repeatedly forced civilizations to confront difficult questions about life, belief and meaning. The development of a synthetic, embryonic lifeform is no different.

The potential here to expand human understanding and change human life is amazing. Let’s embrace it.

Dr Norman Lewis is managing director of Futures Diagnosis and a visiting research fellow of MCC Brussels.