Use epiphyseal fusion.  Silver 1969 has a good chart I seem to recall.

Also, do you have supporting documentary information indicating that
the remains are sheep?  Sheep are notoriously difficult to
differentiate from goats skeletally, so you might want to tread
cautiously unless you have external supporting evidence.

The status of lamb vs mutton has a lot to do with the end goal of
husbandry practices.  Check articles on kill-off patterns.  Payne 1973
is a classic and talks specifically about sheep/lamb kill off
patterns.

Check out these for more info:

Payne, Sebastian
Kill-off Patterns in Sheep and Goats: The Mandibles from Aşvan Kale.
In Anatolian Studies
Vol. 23, Aşvan 1968-1972: An Interim Report (1973), pp. 281-303

SILVER, I.A. 1969: The Ageing of Domestic Animals. In Brothwell, D.R.
and Higgs, E.S. (eds.), Science in Archaeology: A Comprehensive Survey
of Progress and Research (London), 283−302.

Good luck!

Dessa


On Fri, Dec 28, 2012 at 4:48 PM, geoff carver <[log in to unmask]> wrote:
> You should be able to tell age by whether or not the epiphyses on long bones
> have fused.
>
> -----Original Message-----
>
>
> The difference between the two is that "lamb" typically refers to a young
> sheep under 12 months old which has no permanent incisor teeth, whereas
> "mutton" refers to sheep older than a year, who have more than two permanent
> incisors.  Of course, what we found are butchered bones, without teeth, so
> this distinction seems somewhat difficult.