Examination of Fe and Cu Isotope Variation in Great Apes Using an Optimized Protocol

Abstract

Rationale

Iron deficiency plagues reproductive-aged women across the world, and blood loss during menstruation is proposed as the driving force. To assess if other factors related to reproduction influence Fe and Cu isotope variation in females, we measured Fe and Cu isotope compositions in the bones of chimpanzees and bonobos.

Methods

To do this, we optimize the protocol for isolating Fe and Cu (and Zn) from phosphate-rich skeletal materials for further analysis via MC-ICP-MS. Then, we address possible Fe and Cu variation sources in non-menstruating apes (n = 26, of which the sex of 10 was obtained by DNA analysis).

Results

The optimized method reduced acid volume by ~14%, and sample preparation time by ~37.5%. We did not find significant sex differences in δ⁵⁶Fe values (Δ⁵⁶Fe_f-m = 0.13‰) or δ⁶⁵Cu values (Δ⁶⁵Cu_f-m = 0.33‰).

Conclusion

Given the similar Δ⁵⁶Fe_f-m values between non-menstruating apes and humans, reproductive investment, instead of menstruation alone, is a key factor that drives Fe deficiency in reproductive-aged women and is important to consider with proxies of iron status. Our optimized protocol provides an effective method for exploring iron status in other mammalian species.