Emergence in biology

Emergence is one of the most important concepts developed by scientists in the second half of the twentieth century. Largely, independently of one another emergence was discussed, debated, and developed by physicists, biologists, social scientists, and philosophers.

Biology concerns phenomena at many different scales, some of which are nicely captured in the figure below, taken from here. At each scale, distinct phenomena emerge, with associated concepts, theories, and methods.

Ernst Mayr was one of the leading evolutionary biologists in the twentieth century and was influential in the development of the modern philosophy of biology. He emphasised the importance of emergence, contrasting the value of analysis with the limitations of reductionism (both defined below).

In Mayr's book, What Makes Biology Unique? Considerations on the Autonomy of a Scientific Discipline, chapter 4 is Analysis or Reductionism. 

Needless to say, the workers in the more complex branches of science saw in this [reductionist] claim only a ploy of the chemists and physicists to boost the importance of their fields. As Hilary Putnam said correctly: “What [reductionism] breeds is physics worship coupled with neglect of the ‘higher-level’ sciences. Infatuation with what is supposedly possible in principle goes with indifference to practice and to the actual structure of practice” (1973). 

What is the crucial difference between the concepts analysis and reduction? The practitioner of analysis claims that the understanding of a complex system is facilitated by dissecting it into smaller parts. Students of the functions of the human body choose as their first approach its dissection into bones, muscles, nerves, and organs. They make neither of two claims made by the reductionists 

(A) that the dissection should proceed “down to the smallest parts,” – i.e., atoms and elementary particles, and 

(B) that such a dissection will provide a complete explanation of the complex system. 

This reveals the nature of the fundamental difference between analysis and reduction. Analysis is continued downward only as long as it yields useful new information and it does not claim that the “smallest parts” give all the answers. 

... the view that composite wholes have properties not evident in their components has been widely accepted since the middle of the nineteenth century. The principle was already enunciated by Mill, but it was Lewes (1875) who not only presented a thorough analysis of the topic but also proposed the term emergence for this phenomenon.  

... emergence is characterized by three properties 

... first, that a genuine novelty is produced – that is, some feature or process that was previously nonexistent; 

second, that the characteristics of this novelty are qualitatively, not just quantitatively, unlike anything that existed before; 

third, that it was unpredictable before its emergence, not only in practice, but in principle, even on the basis of an ideal, complete knowledge of the state of the cosmos.

Mayr then discusses how in the first half of the twentieth century, emergence fell out of favour with biologists, such as J.B.S. Haldane, partly because the three characteristics above "appear at first sight to be in conflict with a straightforward mechanistic explanation."

How does this history relate to Phil Anderson and condensed matter physics?  This is nicely discussed by Andrew Zangwill in Chapter 12 of Mind over Matter. More is Different (1972) did not include the word emergence and Anderson did not use the term in print until 1981. Following Anderson's Nobel Prize in 1977, he received many invitations to speak to groups outside the physics community, including biologists, some of whom were fans of "More is Different".  This then exposed Anderson to the thinking and terminology of the biologists.

Aside: In a previous post, I discussed how Mayr described how prominent physicists such as Bohr and Schrodinger embraced vitalism.