Dr Francesca Merlin from the IHPST (CNRS, Paris) gave a talk based on her forthcoming paper which evaluates recent calls to extend our notion of inheritance. She starts with a commonsensical notion of inheritance as 'like begets like' and claims that the notion of inheritance is intended, primarily, to explain the fact that organisms produce organisms that are similar to them. It grounds continuity across generations of living things, in other words. She argues, thus, that there is a privileged link between inheritance and reproduction.
After reviewing various proposals for expanding our definition of inheritance, she claims that many make the mistake of confusing the acquisition of variation from its transmission. A one-off transfer of some causal effect is not enough, she argues, to ground the all-important capacity for evolution by natural selection. The transfer or transmission must be recurrent...otherwise it is mere acquisition of variation.
Furthermore, Merlin argues against the possibility of horizontal inheritance. Since reproduction is always a vertical relation, horizontal transfer should be considered as mere infection, not inheritance.
Finally she argues, with Griesemer, for the necessity of material overlap in instances of reproduction. But the overlap must be internal to the organism - money may be materially transferred across generations, but because it is outside it can only qualify as transmission, not as inheritance.
Merlin thus aspires to retain a notion of inheritance that stays close to paradigmatic biological cases. Reproduction does involve the inheritance of more than mere genes....but we shouldn't go too far and include external factors, or things that are passed to organisms that are not the offspring.
Merlin's talk is followed by a response from Matthew Clark, a postgraduate student who is halfway through a BPhil in Philosophy at the University of Oxford. Clark is sympathetic to some of the distinctions Merlin drew - for example between inheritance and the shared, recurring experience of persistent resources such as sunlight. But he would prefer a more permissive extension of our notion of inheritance, one that includes beaver's dams as inherited properties, that allows the parent-offspring relation to apply to relations of cultural influence, and that permits things like prions to inherit things even though there is no material overlap in prion replication. In general, Clark is not convinced that inheritance has to be tied to any standard or paradigm reproductive event, and prefers to see Merlin's definition as capturing a prevalent or often-observed form of inheritance, than as providing necessary conditions for it.
You can listen to the whole talk and response here. The response starts at 40 mins 17.
Next post: Powers and Clarke - Institutions and the development of human sociality.