I was wondering about this. My guess at average lifespans for playable races is:

Altmer: 1000 years (purest descendants of Aldmer)
Argonian: 150 (reptilian nature and poison/disease immunity)
Bosmer: 700 (due to some human ancestry)
Breton: 200 (due to trace Elven ancestry)
Dunmer: 850
Imperial: 150 (purest human blood of Tsaesci)
Khajiit: 75 (cats don't live long)
Nord: 100 (probably shorter due to drunken bar fights)
Orsimer: 100 (they are cursed Elves)
Redguard: 100

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I'm guessing the Dwemer lived probably upwards of 2000 years or more due to their advanced technology and magic.

Falmer probably live 40 or so years due to their harsh living conditions and primitive behavior. The Snow Elves (AKA the non-primitive Falmer) probably live around 900 years.

Tiber Septim lived to be only 108 years old and is the oldest Human Tamiral has ever seen.

It's funny because the oldest person ever to live on Earth was 122 years old.

Yeah, 100 average for all human races is pushing it. They are human. They're like you and I with the major difference being that we're never really worried about having someone jam the business end of a greatsword down our throats.