To date, no agreement has been reached on the definition of taxonomic categories such as species,

genus and family. This means that there are no generally accepted definitions for terms that

biologists deal with on a daily basis.

The authors of Basic Types of Life draw attention to the previously little-noticed possibility of

characterizing kinship relationships in an experimentally verifiable manner through interspecific

crossings. The genetically based Basic Type category based on this is superior to the species category

and, in the case of the organisms from the animal and plant kingdoms studied so far, lies between

genus and family. Basic Types represent clearly demarcated groups.

Species concepts are usually based on the assumption that speciation is correlated with

development from a lower to a higher order. By contrast, the distribution of characteristics within

the species ranges of individual Basic Types is interpreted within the framework of the hypothesis of

genetically polyvalent ancestral forms from which genetically less flexible descendants have arisen

through speciation processes.

Basic Types of Life is a translation of the German classic biological work, Typen des Lebens. This

translated volume also incorporates new hybridization and other data that sheds further light on

previous studies.