Testing the expensive-tissue hypothesis' prediction of inter-tissue competition using causal modelling with latent variables - UTU Research Portal

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Testing the expensive-tissue hypothesis' prediction of inter-tissue competition using causal modelling with latent variables

Authors: Bezerra, Meghan Shirley; Helle, Samuli; Seunarine, Kiran K.; Arthurs, Owen J.; Eaton, Simon; Williams, Jane E.; Clark, Chris A.; Wells, Jonathan C. K.

Publisher: CAMBRIDGE UNIV PRESS

Publishing place: CAMBRIDGE

Publication year: 2024

Journal: Evolutionary Human Sciences

Journal name in source: EVOLUTIONARY HUMAN SCIENCES

Journal acronym: EVOL HUM SCI

Article number: e33

Volume: 6

Number of pages: 18

eISSN: 2513-843X

DOI: https://doi.org/10.1017/ehs.2024.26

Web address : https://doi.org/10.1017/ehs.2024.26

Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/458666070

Abstract

The expensive-tissue hypothesis (ETH) posited a brain-gut trade-off to explain how humans evolved large, costly brains. Versions of the ETH interrogating gut or other body tissues have been tested in non-human animals, but not humans. We collected brain and body composition data in 70 South Asian women and used structural equation modelling with instrumental variables, an approach that handles threats to causal inference including measurement error, unmeasured confounding and reverse causality. We tested a negative, causal effect of the latent construct 'nutritional investment in brain tissues' (MRI-derived brain volumes) on the construct 'nutritional investment in lean body tissues' (organ volume and skeletal muscle). We also predicted a negative causal effect of the brain latent on fat mass. We found negative causal estimates for both brain and lean tissue (-0.41, 95% CI, -1.13, 0.23) and brain and fat (-0.56, 95% CI, -2.46, 2.28). These results, although inconclusive, are consistent with theory and prior evidence of the brain trading off with lean and fat tissues, and they are an important step in assessing empirical evidence for the ETH in humans. Analyses using larger datasets, genetic data and causal modelling are required to build on these findings and expand the evidence base.

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Funding information in the publication:
National Institute for Health Research, grant/award number NIHR-CS-012-002 (OJA); Wenner–Gren Foundation Dissertation Fieldwork Grant, grant/award number 8888 (MSB); Strategic Research Council, grant/award number 345183 (SH); Academy of Finland, grant/award number 317808, 320162, 325857, and 331400 (SH).