It is literally my job to study the spread of disease. At this point, with the current evidence, the only plausible scenario is the the virus moved from an animal to human. I’m not sure what you mean by “evolved in nature”, but what we’re certain about at this point is that the virus is zoonotic in origin, which means it’s present in animals. The question is where/when the leap to humans occurred. The original hypothesis was that it occurred at a market in Wuhan. That may still be the case. Based on the epidemiological evidence we have so far, it’s actually pretty likely that it made this jump several times in late 2019. We know that there were infections in North America and Europe before December 2019, so it was circulating in humans for a while before the big outbreak. Was one of the original infected humans a lab worker in Wuhan? Maybe, it’s as likely as anything else. Did the infection jump to humans from animals that were being studied in the lab? Maybe, but so far there’s no evidence. Also, like I said, because the virus was circulating for some time in geographically diverse areas, it’s likely that this jump occurred several times.