How did they manage to get UNAM to approve and publish such a report?:
With Maussan's track record one has to wonder a bit. He was involved with the so called Nazca tridactyl mummies and a university in Peru. Some professors from that university, Universidad Nacional San Luis Gonzaga (UNICA/UNSLG), wrote a paper on some of the specimens and it's been implied ever since that the university is deeply involved in these mummies. This seems to be a trick Mausson uses often, getting a few people from a legit university, government agency or company and using this to suggest more involvement than is really happening.
In the case of UNICA and the tridactyl mummies, the anthropology and archaeology departments were NOT involved in the paper as would be expected, rather the lead author was a public health professor along with a dentist and other non-anthro people. Note that Huaripaucar, Aviles, Canales and Vizarreta are all listed as being affiliated with UNICA/UNSLG. However, Aviles and Vizarreta use Gmail accounts as if they didn't even have university email accounts:
The actual anthropology students at UNICA put out a statement distancing themselves from the paper and the mummies claiming it was a few professors/administrators working with Mausson and other local grifters looking for notoriety. I'll have to find it in another thread.
As for UNAM, some people there have worked with Mausson before, including on the Nazca mummies. I think Mausson is still a big deal for certain people in Mexico and he has connections. As in the UNICA case, it may be some people from UNAM working with Mausson, making it look like the university is more involved than it is.