2012 interview with Peter Richerson

6:10 has Richerson's discussion of "cultural units". He says:

There's this idea that has been promoted, particularly by Richard Dawkins that inherited systems have to be digital - the way genes are supposed to be - that there have to be discrete units that are potentially infinitely long lived - and Rob Boyd and I think this is not correct actually - you can have "unitless" evolution without any trouble really.

I'm pretty sure this is a misunderstanding. What Dawkins said (in "River Out Of Eden", page 19) was:

Only a digital genetic system is capable of sustaining Darwinism over eons of geological time.

The idea that I think Dawkins was getting at here is that evolving systems "go digital" after a little while, and discover the advantages of digital transmission. Genes went digital this before DNA was invented, and many types of meme went digital before computers were invented - in what is known as the digital revolution. They key driver of these transitions is attaining better copying fidelity - and thus gaining the ability to maintain the integrity of a larger genome.

Richerson attacks the idea that everything that is inherited is digital - but that claim seems to be a very silly one. I don't think that is a claim that Dawkins ever intended - or would endorse. Indeed, Dawkins himself gives examples of low-fidelity cultural transmission in the same chapter, namely: audio tape recorders and photocopying (see page 16).