However, I notice that some sources differ - confining the idea of "heredity" further. The Encyclopedia Britannica is explicitly DNA-gene centric:here:
heredity: the sum of all biological processes by which particular characteristics are transmitted from parents to their offspring. The concept of heredity encompasses two seemingly paradoxical observations about organisms: the constancy of a species from generation to generation and the variation among individuals within a species. Constancy and variation are actually two sides of the same coin, as becomes clear in the study of genetics. Both aspects of heredity can be explained by genes, the functional units of heritable material that are found within all living cells.Reference.com confines the idea of heredity even more - to organisms that experience meiosis - with this:
heredity:the transmission of genetic characters from parents to offspring: it is dependent upon the segregation and recombination of genes during meiosis and fertilization and results in the genesis of a new individual similar to others of its kind but exhibiting certain variations resulting from the particular mix of genes and their interactions with the environment.
These sources are simply wrong. However, their mistake is widespread and leads to confusion about cultural evolution. For example, Larry Moran defines evolution using the term 'heredity' - saying: "Evolution is a process that results in heritable changes in a population spread over many generations." - and then goes on to argue that:
I've already alluded to one of the classic questions that a proper definition can answer — the increased height of Europeans over the past five centuries. Armed with a good definition of biological evolution we can focus on one of the key requirements; namely, heritable change. It turns out that the increase in height is due to a better diet and not to genetic changes. Therefore, this is not evolution according to the scientific definition.
This is a serious conceptual mistake. European diet has improved (largely) through memetic evolution. Memes are passed from one generation to the next in cultural evolution - and rather obviously this should meet any sensible scientific definition of evolution - as is attested to by the now-massive literature on cultural evolution. Yet Moran dismisses it - apparently due to his conception of the definition of the term 'heredity'. This seems like a spectacular mess to me.
Larry is not alone in this evolutionary denialism. Here's Mark Ridley on why cultural evolution doesn't qualify as being "evolution":
Changes that take place in human politics, economics, history, technology and even scientific theories are sometimes loosely described as evolutionary. In this sense "evolutionary" means mainly that there has been change over time - and perhaps not in a preordained direction. [...] human ideas and institutions can sometimes spit during their history - but their history does not have such a clear-cut branching tree-like structure as does the history of life. Change and splitting provide two of the main themes in evolutionary theory.
His complaint appears to be that cultural evolution is too reticulated - one of the most dopy objections to cultural evolution ever - once you consider how reticulated bacterial evolution is.
Anyway, these days, almost everyone agrees that cultural evolution is a type of evolution. The remaining debate in the area is mostly over whether cultural evolution is Darwinian. However we obviously have a mopping-up operation to do - as some folk don't even regard cultural evolution as being a type of evolution! That position seems indefensible to me.