The scene is, in fact, meant to be that of prehistoric Earth; not just millions of years, but around some 540 million years ago (give or take several million), during a period known as the "Cambrian Explosion", when some 98% of ancestors of all present-day terrestrial life first came to be. Some of it can be seen amid that ancient volcanic landscape - small greenish and yellowish plants, some early mossy-like microbial mats, and even a few trilobites swimming about at the edges of the mineral-rich waters.
But this early Earthly life isn't alone - there are visitors from across space, surveying the planet and trying to learn what they can about the origins of life by studying it in-progress on different worlds. One of them has left the safety of the saucer - it's actually bigger than it looks, and much farther away too - to examine the signs of life in an around the water, and see what information might be gleaned for a thesis about the formation of life from lifelessness...On Abiogenesis.
Cool concept and beautiful pic.
As for the pic's alien visitors though, if they wanted to study abiogenesis on Earth they arrived WAY too late. By the time of the "Cambrian Explosion", the origins of life on Earth already lay more than 3 billion years in the past (the oldest known evidence for life on Earth is about 3.8 billion years old). Even multicellular life was old news at this time as multicellularity goes back at least 1 billion years before our time, and thus nearly half a billion years before the Cambrian, and perhaps even further (there are indications evolution on Earth may have been experimenting with multicellularity as far back as 2.5 billion years ago).
Still, if the aliens want to study early stage complex ecosystems then perhaps they've come to the right place. IIRC, the Cambrian has Earth's earliest unambiguous evidence of things like predator-prey relationships, ecological specialisations and so on. It even possibly had the first cases of animals taking their first steps onto land in the form of some extinct marine arthropods able to leave the water for a bit, though it would still be a while before Earth got its first truly terrestrial creatures.
Thank you for your comments.
Yes, admittedly the title is out by a few billion years, but when I came up with the title I thought it sounded pretty cool, and was also short and snappy. Just as you say, life actually began much earlier, shortly after the end of the Late Heavy Bombardment around 3.8 billion years ago in the Archean Era, but that would make for a less interesting picture because a) there wouldn't be any visible signs of life at our everyday scales, and b) the Earth itself could also be too unstable still for alien survey craft to even land. Not to mention there wouldn't be very much in the way of land to land on at that time either. So yeah, I was taking a liberty there with the title.
Another thing actually, is that just because they're trying to study the origins of life on other planets, doesn't mean they're going to arrive at the right time - they're looking around at a whole variety of planets, examining life in various different stages of formation, some might be at just the right point while others like Earth are rather more advanced. As (like us) they don't have the lifespan to just sit and watch evolution take place, seeing different stages of the process playing at on different worlds would still help to build up a much more complete picture of the theories of evolution.