Fishing for iodine: what aquatic foraging by bonobos tells us about human evolution

Abstract

Background: Expansion of brain tissue and development of advanced cognitive skills are characteristic traits of human evolution. Their emergence has been causally linked to the intake of nutrients that promote brain development and iodine is considered a critical resource. Rich sources of iodine exist in coastal areas and evolutionary scenarios associate the progressive development of brain size and cognitive skills to such landscapes. This raises the question of how early hominins living in continental areas could have met their iodine requirements. One way to explore this question is to use information from hominoid primates as a proxy for the nutritional ecology of early hominins. Bonobos are particularly interesting in this context as they are restricted to the central part of the Congo basin, an area considered to be iodine deficient based on human standards. Methods: Pooled samples of fruit, terrestrial and aquatic herbs were used to assess mineral content with an inductively coupled plasma optical emission spectrometer. Iodine content was measured with the catalytic technique of Sandell-Kolthoff and two separate inductively coupled plasma mass spectrometry methods. Results: Nutritional analyses revealed that the mineral content of aquatic herbs is higher than in other plant foods. Moreover, two species of aquatic herbs consumed by bonobos contain iodine concentrations that are almost equivalent to marine algae. Conclusions: These data challenge the general notion that the Congo basin is iodine deficient and demonstrate that its lowland forest offers natural sources of iodine in concentrations high enough to prevent iodine deficiency in hominoids and humans.

Importance of subterranean fungi in the diet of bonobos in Kokolopori

“…Alternatively, fungi may be consumed as a source of particular micronutrients and minerals. In particular, we found notably high sodium concentration in our H. bonobo samples relative to other plant foods that constitute major part of ape diet (Grueter et al, 2018;Hohmann et al, 2019;Reynolds et al, 2009; see Table 3). It is therefore plausible that bonobos consume fungi such as H. bonobo to supplement their diet with sodium.…”

“…In particular, it has been proposed that the availability of fallback food plays an important role in influencing the geographic and temporal distribution of many primate species (Grueter et al, 2009; Marshall et al, 2009), and the need to acquire specific nutrients can have important influence on their ranging and feeding behavior (e.g. Bogart & Pruetz, 2011, Grueter et al, 2018, Hanson et al, 2003, Hohmann et al, 2019, Matsubayashi et al, 2011, Reynolds et al, 2009).…”

“…Examples of nonstaple food items include meat (Fedigan, 1990;Surbeck et al, 2009;Watts, 2020) and insects (Bogart & Pruetz, 2011;McGrew, 2014;Webster et al, 2014) for primates, salty rocks and soil for elephants and ungulates (Holdø et al, 2002;Lundquist & Varnedoe, 2006), as well as fungi and seeds for some rodents (Markova et al, 2020). A nonstaple food item may function at times as fallback food, that is, food consumed in periods when the preferred food is scarce (Marshall & Wrangham, 2007;Watts et al, 2012), or as a source of particular nutrients needed to meet specific dietary requirements (Hohmann et al, 2019;Lundquist & Varnedoe, 2006).…”

EstimatingPanevolutionary history from nucleotide site patterns

“…Chimpanzees have been characterized as poor swimmers (Angus 1971) and as being afraid of water (Kano 1992), yet some populations enter bodies of water to forage (Watts et al 2012a;Watts et al 2012b) and thermoregulate in hot, dry habitats (Pruetz and Bertolani 2009). Interestingly, bonobos are not characterized as having this aversion to water (Kano 1992) and are known to routinely forage in swamps (Uehara 1990;Hohmann et al 2019). The geographic distribution of Pan prompted early speculation that the formation of this river, which was dated at the time to ~1.5 -3.5 Ma, coincided with or prompted speciation in this genus (Horn 1979;Beadle 1981;Myers Thompson 2003), which was estimated to be younger than 1.5 Ma by a number of early genetic studies (Won and Hey 2005;Becquet and Przeworski 2007;Caswell et al 2008, but see Stone et al 2002;Yu et al 2003;Wegmann and Excoffier 2010).…”

Reinterpreting patterns of variation in human thyroid function

“…Certain food items rich in iodine such as seaweed, sea food, dark green leafy vegetables, egg yolk, and seeds, were probably more common in our ancestral diets [ 22 ]. In seemingly iodine-depleted regions, such as the Congo basin, the consumption of iodine-rich aquatic plants has even been reported in non-human primates [ 116 ]. However, an increased consumption of cereal grains, legumes, and tubers associated with the adoption of agriculture may have heightened our ingestion of substances that interfere with our body’s ability to utilize dietary iodine effectively, also known as goitrogens [ 117 ].…”