Hans Adolf Driesch | Biography

The work of Hans Driesch work was a critically important antecedent to the animal cloning experiments of the late 20th century. Driesch was born in Bad Kreuzsnach, Germany. He studied at Freiburg with August Weismann and then at Jena where he received his Ph.D. with Ernst Heinrich Haeckel in 1889. Prior to Driesch, another German biologist Wilhelm Roux, showed that a half embryo develops when one cell of a two cell frog embryo is killed. This suggested that the embryo is a mosaic and that cells develop independently. Further, it implied that the genetic material contained in the nucleus is qualitatively unequally divided. Thus, embryonic cell division would resulting in differential distribution of the genetic material. Driesch, using sea urchin eggs, obtained diametrically different results. He separated embryonic cells (blastomeres) at the two cell stage and found that each of the cells cleaved (divided), formed ciliated blastulae, and subsequently developed into perfect but miniature pleuteus larvae. The isolated cells were viewed as a "harmonious equipotential system" meaning that they ordinarily developed harmoniously, when naturally together, to give rise to a normal pleuteus larva but when separated, they evidenced that they were equipotential, i.e., each could give rise to an entire pleuteus larva. Using modern terminology, it would be said that the genetic material (DNA) was not divided, but it replicated with cell division in the two cell stage embryo.

How long in development does complete genetic potential persist, i.e., how long do embryonic cells remain totipotent, with replication of the entire DNA genome, during development? This was the question raised by the pioneer animal cloners Robert Briggs and Thomas J. King of Philadelphia when they reported the first successful animals produced by cloning from embryonic nuclei. More recently, Ian Wilmut in Scotland, and others, have cloned mammals from adult nuclear donors. Obviously, totipotentiality exists in at least some cells of the adult.

The fact that Driesch got whole organisms from half embryos caused him to seriously doubt the prevailing notion that life could be explained in terms of physics and chemistry. Driesch could not envision a mechanism that could divide and reconstitute itself into two whole mechanisms. He believed this was impossible following the principles of physics and chemistry. Because of this, Driesch adopted a vitalistic view of development, becoming one of the last proponents of vitalism, which proposed that the principles of physics and chemistry are inadequate to explain living phenomena and therefore, there must be a vital force or "entelechy" which guides development.

Driesch abandoned experimental embryology altogether and spent his later years studying philosphy. His liberal views, desire for peace, and lack of sympathy for the Nazi regime resulted in his forced retirement in 1933. While retired, Driesch continued his philosophical studies until his death at the age of in 73.