Unknown
- Life' Proteins
There is, however, another problem that confronts evolutionary theory. There are over 100 amino acids, but only 20 are needed for life's proteins. Moreover, they come in two shapes: Some of the molecules are "right-handed" and others are "left-handed". And there is no known reason why either shape should be preferred in living things. Yet, of the 20 amino acids used in producing life's proteins, all are left-handed!
