I'm in the process of playing through (judging by the tree, probably around 80+ or even 90+ percent completion) and while it wasn't confirmed 100 percent because it was only speculation from the main characters, they were betting that the body was that of the previous scientist/doctor, the predecessor of one of Beck's mothers.

I believe the name was Dr Prescott, the employee that Nelly Moedwill took over for.

引用自 Ink Hyaena：

I believe the name was Dr Prescott, the employee that Nelly Moedwill took over for.

^ this.
He was sabotaging his notes after he understood what they were doing. He tried to slow them down as much as possible, but he got caught.

Just finished the game and I can confirm like other comment said. That man suppose to be Dr Prescott. 1 thing I just kinda disappointed or rather raise question is that it doesn't giving explanation how they do the source in true ending.