I had lots of “luck” on my reading of the Tevis ride for statistics.
http://www.teviscup.org/
This link is for the horses and riders. There is alot of detail on this site. Start with history and you can see some times, and MANY other stats. Endurance riders are all about stats. It is real data, not fake.
For runners of the human kind, look at this site and once again click on the history and you will find all kinds of info.
http://www.wser.org/history-year-by-year/
To compare the two sport events you have to find out if the trail was exactly the same, and also if the weather was the same.
Also, did the runner traverse Cougar’s Rock?
I have ridden endurance horses for many years. It is amazing what a horse can really do. On this particular ride, there is pretty much a set speed you need to keep your horse doing or you will not make a cut off time. Lots of those horses do a high speed of 10 mph or more the entire ride. Not sure a human could do that in high heat, adverse trail conditions, etc. Maybe. I haven’t looked at the stats on the human side of this.
You really have to compare the same footing for each, and weather. Also, humans do not carry any weight, so not sure how you factor that in. Not sure if humans have vet checks, or not along the way.
You can also check:
www.aerc.org for more endurance ride results. Just go to the menu and look up ride results for that ride. You can get them for many many years back. Check the Old Dominion ride also. It is another 100 miler and very tough with the humidity and heat.
Good luck.