I'm reading Being and Time and have got to the passage where Heidegger says
[...] we are to destroy the traditional content of ancient ontology until we arrive at those primordial experiences in which we achieved our first ways of determining the nature of Being - the ways that have guided us ever since.
This sounds like we a quest for, and you'll have to excuse my vagueness here, the "first instance" of Dasein. One of Heidegger's students, Hans Jonas, discusses something that sounds similar in Phenomenon of Life
Jonas talks about man's ability to form images and how this relates to man's ability to form an image of himself. He claims that this ability is a defining characteristic of humanity and cites cave paintings, such as those a Altamira, as the first evidence of humanity as distinct from the rest of life.
Jonas' conception of "life" and Heidegger's "Being" are supported by very different arguments, but Jonas' claim that "life can only be known by life" and Heidegger's description of Dasein where it is "being in such a way that one has an understanding of Being" seem to share the same character. In summary, they both talk about something similar
MH) Being that can enquire into the nature of Being HJ) Life that can view itself abstractly
The two ideas are obviously related genealogically, but this does not mean they mark out the same thing. Life and Being seem to be different things in general, but is Jonas' humanity, and Heidegger's Dasein the same? If so, does Dasein begin with the making of images?