I'm in the hall of Planet Earth, and I'm standing before one of my favorite samples in this exhibit, a stromatolite. Now it's an interesting question when life first appeared on Earth. There's some chemical evidence that life appeared as early as 3.8 billion years. Ago. But the fossil record doesn't start until about 3.4 to 3.5 billion years ago. And the fossil record from that time until perhaps 600 million years ago is entirely of microbial organisms. Primarily of organisms known as Stromatolites. And this is a fossil Stromatolite. Stromatolites, at least the ones that see growing today exist in tidal pools, and basically they're colonies of microbes that build these sort of organo-sedimentary structures that have you know, real structures. You know, this one has been cut open, and you can see the structure. inside this one. that grow in very shallow water. In other words, they grow in the photic zone. in looking at fossil stromatolites. And in studying the nature of the sediments around them. Their structures, such as the presence of, of ripple marks, and the like. Indicates that these stromatolites, the fossil stromatolites also lived in shallow water. In other words, in the photic zone. And the theory is that these organisms, like the present day organisms, therefore. Engaged in photosynthesis. So this is very interesting, and there're important implications of that. If at 3.4 billion years, we had already established photosynthetic organisms, it means that life was actually fairly complex and must have started well before that. So this particular stromatolite came from Morytania. It actually is not a particularly old stromatolite as fossil stromatolites go. It probably grew about 900 million years ago in the shallow waters on the West African platform. Stromatolites are characterized by these kinds of structures with a conical. Sadder, and branches growing out. Probably the way this happened was that the microbes were growing here and as they as they grew they precipitated carbonate minerals around them. And these simply grew, and grew, and grew with time. eventually these stromatolites were covered with mud and fossilized.