The following article argues for defining the beginning of human life by using systems biology. While this definition places human life's beginning at a point earlier than implantation, Yeung brings up some thought-provoling points on fertilization and twinning. Another example of the breadth of opinions on this topic.

Ethics and Medicine, Summer 2005
By Patrick Yeung, Jr.


Many arguments put forward for when human life begins. To simplify the debate, some claim human life begins at fertilization, while others say that human life begins at implantation. While both events are significant in the early development of human life, neither offers a complete answer to the question of the beginning of human life.

I will argue for a definition of the beginning of human life that uses concepts taken from systems biology, and will apply this definition to the current debate on somatic cell nuclear transfer and embryonic stem cell research.

Systems biology, an emerging field of research that seeks to understand the fundamental principles of living systems, has sought to distinguish an organism from a cell. In so doing, it offers us two important insights that are particularly helpful in determining when human life begins. First, systems biology recognizes that an organism is an independent, embodied process; that is, a single unified whole that manifests itself in various ways over time. Second, systems biology holds that an organism is a determined system that actively follows a particular trajectory. It is not passive, and does not require outside intervention to develop. Together, these two insights help differentiate static cells from dynamic organisms. An organism, then, can be defined as a distinct embodied process that actively follows a particular trajectory. If that trajectory is ever manifest in ways considered human, then the organism from the beginning is human.

When, then, does human life begin?

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