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

Area of Science:

• Paleoproteomics and Bioarchaeology
• Primate Biology and Evolution
• Human Health and Nutrition

Background:

• Iron deficiency is a global health issue affecting reproductive-aged women, with menstrual blood loss often cited as the primary cause.
• The influence of other reproductive factors on iron (Fe) and copper (Cu) isotope variations in females remains underexplored.

Purpose of the Study:

• To investigate if reproductive factors beyond menstruation affect Fe and Cu isotope variations in female primates.
• To optimize a protocol for analyzing Fe and Cu isotopes in phosphate-rich skeletal materials.

Main Methods:

• Developed and optimized a protocol for isolating iron, copper, and zinc from bone phosphate using reduced acid volumes and preparation time.
• Analyzed Fe and Cu isotope compositions (δ⁵⁶Fe and δ⁶⁵Cu) in skeletal samples from non-menstruating chimpanzees and bonobos (n=26).
• Utilized multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for precise isotopic measurements.

Main Results:

• The optimized protocol significantly reduced acid consumption (~14%) and sample preparation time (~37.5%).
• No significant sex-based differences were observed in δ⁵⁶Fe (Δ⁵⁶Fe_f-m=0.13‰) or δ⁶⁵Cu (Δ⁶⁵Cu_f-m=0.33‰) values in the studied apes.
• The findings suggest that factors other than sex or menstruation may influence Fe and Cu isotope ratios.

Conclusions:

• Reproductive investment, rather than menstruation alone, is a critical factor contributing to iron deficiency in reproductive-aged women.
• The study highlights the importance of considering reproductive investment when assessing iron status using isotopic proxies.
• The optimized analytical protocol is effective for investigating iron status in diverse mammalian species.