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Bryant KL, Hansen C, Hecht EE. Fermentation technology as a driver of human brain expansion. Commun Biol 2023; 6:1190. [PMID: 37996482 PMCID: PMC10667226 DOI: 10.1038/s42003-023-05517-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 10/27/2023] [Indexed: 11/25/2023] Open
Abstract
Brain tissue is metabolically expensive. Consequently, the evolution of humans' large brains must have occurred via concomitant shifts in energy expenditure and intake. Proposed mechanisms include dietary shifts such as cooking. Importantly, though, any new food source must have been exploitable by hominids with brains a third the size of modern humans'. Here, we propose the initial metabolic trigger of hominid brain expansion was the consumption of externally fermented foods. We define "external fermentation" as occurring outside the body, as opposed to the internal fermentation in the gut. External fermentation could increase the bioavailability of macro- and micronutrients while reducing digestive energy expenditure and is supported by the relative reduction of the human colon. We discuss the explanatory power of our hypothesis and survey external fermentation practices across human cultures to demonstrate its viability across a range of environments and food sources. We close with suggestions for empirical tests.
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Affiliation(s)
- Katherine L Bryant
- Laboratoire de Psychologie Cognitive, Aix-Marseille Université, Marseille, France.
| | - Christi Hansen
- Hungry Heart Farm and Dietary Consulting, Conley, GA, USA
| | - Erin E Hecht
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA.
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Zhu X, Chen C, Jiang Y, Zhao L, Jin L. Geographical variation of organ size in Andrew’s toad (Bufo andrewsi). Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.972942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Phenotypic variation of morphological and physiological traits is assumed to be generated from spatial heterogeneity in environments, and it has been regarded as an important concern domain in evolutionary biology. Organs display markedly size variation among populations along environmental gradients and this variation is associated with changes in oxygen supply and energy demands. Here, we investigated geographical variation in the relative size of organs (i.e., brain, heart, lung, gallbladder, livers, spleen, kidneys, and digestive tract) among 14 populations of Andrew’s toad (Bufo andrewsi) transcending an elevational range from 864 to 2,367 m, and spanning 8° latitude. We found that although the relative sizes of the eight specific organs varied significantly among populations, none organ size was affected by altitude and latitude. However, based on the combined the new data and published data we found a negative relationship between the relative size of the heart and latitude, contrasting to the Hesse’s rule. We also found that the relative size of livers was positively linked to latitude, suggesting that more energy demands and intakes due to slower metabolism in high latitude shaped the evolution of larger livers.
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Abstract
Abstract
Brain size exhibits significant changes within and between species. Evolution of large brains can be explained by the need to improve cognitive ability for processing more information in changing environments. However, brains are among the most energetically expensive organs. Enlarged brains can impose energetic demands that limit brain size evolution. The expensive tissue hypothesis (ETH) states that a decrease in the size of another expensive tissue, such as the gut, should compensate for the cost of a large brain. We studied the interplay between energetic limitations and brain size evolution in small mammals using phylogenetically generalized least squares (PGLS) regression analysis. Brain mass was not correlated with the length of the digestive tract in 37 species of small mammals after correcting for phylogenetic relationships and body size effects. We further found that the evolution of a large brain was not accompanied by a decrease in male reproductive investments into testes mass and in female reproductive investment into offspring number. The evolution of brain size in small mammals is inconsistent with the prediction of the ETH.
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Relative Mass of Brain- and Intestinal Tissue in Juvenile Brown Trout: No Long-Term Effects of Compensatory Growth; with Additional Notes on Emerging Sex-Differences. FISHES 2018. [DOI: 10.3390/fishes3040038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study investigated whether compensatory growth causes long-term effects in relative brain- or intestine size in a wild, predominantly anadromous, population of brown trout (Salmo trutta). The subject fish belonged to two treatment groups; one group had undergone starvation and subsequent growth compensation, while the other were unrestricted controls. The main hypothesis that compensatory growth would negatively affect brain and intestinal size, as a consequence of growth trade-offs during the compensatory phase, could not be supported as no significant differences were detected between the treatment groups. Further exploratory analyses suggested that males and females started to diverge in both brain and intestine size at around 130 mm fork length, with females developing relatively smaller brains and larger intestines. The size at which the differences appear is a typical size for smoltification (saltwater preadaptation), and females tend to smoltify to a higher proportion than males. Smoltification is known to cause a more elongated morphology and relatively smaller heads in salmonids, and the marine lifestyle is associated with rapid growth, which could require relatively larger intestines. Hence, these emerging sex differences could be a consequence of sex-biased smoltification rates. An investigation of wild smolts of both sexes indicated no differences in brain or intestine mass between male and female smolts.
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Huang CH, Yu X, Liao WB. The Expensive-Tissue Hypothesis in Vertebrates: Gut Microbiota Effect, a Review. Int J Mol Sci 2018; 19:E1792. [PMID: 29914188 PMCID: PMC6032294 DOI: 10.3390/ijms19061792] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 05/28/2018] [Accepted: 06/12/2018] [Indexed: 02/08/2023] Open
Abstract
The gut microbiota is integral to an organism’s digestive structure and has been shown to play an important role in producing substrates for gluconeogenesis and energy production, vasodilator, and gut motility. Numerous studies have demonstrated that variation in diet types is associated with the abundance and diversity of the gut microbiota, a relationship that plays a significant role in nutrient absorption and affects gut size. The Expensive-Tissue Hypothesis states (ETH) that the metabolic requirement of relatively large brains is offset by a corresponding reduction of the other tissues, such as gut size. However, how the trade-off between gut size and brain size in vertebrates is associated with the gut microbiota through metabolic requirements still remains unexplored. Here, we review research relating to and discuss the potential influence of gut microbiota on the ETH.
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Affiliation(s)
- Chun Hua Huang
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China.
- Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong 637009, Sichuan, China.
| | - Xin Yu
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China.
- Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong 637009, Sichuan, China.
| | - Wen Bo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China.
- Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong 637009, Sichuan, China.
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Dornburg A, Warren DL, Zapfe KL, Morris R, Iglesias TL, Lamb A, Hogue G, Lukas L, Wong R. Testing ontogenetic patterns of sexual size dimorphism against expectations of the expensive tissue hypothesis, an intraspecific example using oyster toadfish ( Opsanus tau). Ecol Evol 2018; 8:3609-3616. [PMID: 29686842 PMCID: PMC5901164 DOI: 10.1002/ece3.3835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 12/04/2017] [Accepted: 12/06/2017] [Indexed: 11/09/2022] Open
Abstract
Trade‐offs associated with sexual size dimorphism (SSD) are well documented across the Tree of Life. However, studies of SSD often do not consider potential investment trade‐offs between metabolically expensive structures under sexual selection and other morphological modules. Based on the expectations of the expensive tissue hypothesis, investment in one metabolically expensive structure should come at the direct cost of investment in another. Here, we examine allometric trends in the ontogeny of oyster toadfish (Opsanus tau) to test whether investment in structures known to have been influenced by strong sexual selection conform to these expectations. Despite recovering clear changes in the ontogeny of a sexually selected trait between males and females, we find no evidence for predicted ontogenetic trade‐offs with metabolically expensive organs. Our results are part of a growing body of work demonstrating that increased investment in one structure does not necessarily drive a wholesale loss of mass in one or more organs.
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Affiliation(s)
- Alex Dornburg
- North Carolina Museum of Natural Sciences Raleigh NC USA
| | - Dan L Warren
- Senckenberg Institute for Biodiversity and Climate Frankfurt am Main Germany
| | | | - Richard Morris
- North Carolina Museum of Natural Sciences Raleigh NC USA
| | - Teresa L Iglesias
- Physics and Biology Unit Okinawa Institute of Science and Technology Graduate University Okinawa Japan
| | - April Lamb
- North Carolina Museum of Natural Sciences Raleigh NC USA.,Department of Applied Ecology North Carolina State University Raleigh NC USA
| | - Gabriela Hogue
- North Carolina Museum of Natural Sciences Raleigh NC USA
| | - Laura Lukas
- North Carolina Museum of Natural Sciences Raleigh NC USA
| | - Richard Wong
- Delaware Division of Fish and Wildlife Dover DE USA
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Yang SN, Feng H, Jin L, Zhou ZM, Liao WB. No evidence for the expensive-tissue hypothesis in Fejervarya limnocharis. ANIM BIOL 2018. [DOI: 10.1163/15707563-17000094] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Abstract
Because the brain is one of the energetically most expensive organs of animals, trade-offs have been hypothesized to exert constraints on brain size evolution. The expensive-tissue hypothesis predicts that the cost of a large brain should be compensated by decreasing size of other metabolically costly tissues, such as the gut. Here, we analyzed the relationships between relative brain size and the size of other metabolically costly tissues (i.e., gut, heart, lung, kidney, liver, spleen or limb muscles) among four Fejervarya limnocharis populations to test the predictions of the expensive-tissue hypothesis. We did not find that relative brain size was negatively correlated with relative gut length after controlling for body size, which was inconsistent with the prediction of the expensive-tissue hypothesis. We also did not find negative correlations between relative brain mass and relative size of the other energetically expensive organs. Our findings suggest that the cost of large brains in F. limnocharis cannot be compensated by decreasing size in other metabolically costly tissues.
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Affiliation(s)
- Sheng Nan Yang
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China
| | - Hao Feng
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China
| | - Long Jin
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China
| | - Zhao Min Zhou
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China
| | - Wen Bo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China
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Mai CL, Liao J, Zhao L, Liu SM, Liao WB. Brain size evolution in the frog Fejervarya limnocharis
supports neither the cognitive buffer nor the expensive brain hypothesis. J Zool (1987) 2016. [DOI: 10.1111/jzo.12432] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- C. L. Mai
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education); China West Normal University; Nanchong China
| | - J. Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education); China West Normal University; Nanchong China
| | - L. Zhao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education); China West Normal University; Nanchong China
| | - S. M. Liu
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education); China West Normal University; Nanchong China
| | - W. B. Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education); China West Normal University; Nanchong China
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Liao WB, Lou SL, Zeng Y, Kotrschal A. Large Brains, Small Guts: The Expensive Tissue Hypothesis Supported within Anurans. Am Nat 2016; 188:693-700. [DOI: 10.1086/688894] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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