Embriologia

Reprod Dom Anim 47 (Suppl. 4), 2–6 (2012); doi: 10.1111/j.1439-0531.2012.02105.x ISSN 0936-6768

An Amazing 10 Years: The Discovery of Egg and Sperm in the 17th Century
M Cobb
Faculty of Life Sciences, University of Manchester, Manchester, UK

Contents
The scientific identification of the key components of sexual reproduction – eggs and sperm – took place during an amazing decade of discovery in the 1660s and 1670s. The names of many of the people involved are now forgotten, and yet their work, and the difficulties they faced and the conflicts they endured, resonate strongly to the present day. Despite this period of innovation, the respective roles of egg and sperm remained unclear for another 170 years. Why did this take so long? And what did people think before these discoveries? By tracing the contours of this major milestone in human knowledge, we can also gain insight into our current knowledge, and the boundaries we may be unwittingly trapped by.

Introduction
The 17th century discovery of the role of egg and sperm in reproduction can be traced to two letters, written 7 years apart, each by a remarkable man who is largely forgotten today. Those letters heralded an amazing decade of discovery that eventually shaped the way we now understand life. ´ In April 1665, Melchisedec Thevenot (c.1620–92), a French patron of the sciences, wrote to his friend Christiaan Huygens (1629–95), a Dutch mathematician and astronomer: ‘We took the opportunity provided by the cold of recent months and applied ourselves to dissections and to investigating the Generation of ´ animals’ (Thevenot 1665). The ‘we’ referred to two of ´ ´ ´ Thevenot’s proteges, the Dutchman Jan Swammerdam (1637–1680) and the Dane Niels Stenson (‘Steno’) (1638–86). This was the start of a process of discussion, dissection and experimentation that would soon lead Swammerdam and Steno to the conclusion that all animals – including humans – come from eggs. The second letter was sent 9 years later, in