The Pleistocene shows radiation of species that hitch-hike on environmental manipulation from the Homo lineage

in #anthropocene6 years ago (edited)

C4 grasses, grazers, and fire as a natural resource available to Homo, led to the spread of open grasslands

C4 grasses are competitive in open grasslands, the C4 pathway of carbon fixation lets the grass grow faster, supporting grazers that maintain the open landscape. The spread of C4 grasses in the late Pliocene and Pleistocene occurs at the same time as the Homo lineage appears in the fossil record, and grazing animals also become more and more common. Fire as a natural resource was widely available at the end of the Pliocene from volcanoes around Lake Turkana, no need to learn to rub sticks against one another, use flint, or gather fire from lightning strikes, fire could be picked up from the ground, and used to burn down large areas of forest, providing the bipedal, upright, Australopithecines (adaptation originally from 3-4Ma for swimming) with a habitat that fit their needs, and allowing other species to hitch-hike on that ecological niche.

The horse and C4 grasses in co-evolution on the Danakil block

Equids in Africa shifted from C3-dominated to C4-dominated diet in conjunction with a global expansion of C4 biomass during the Late Miocene (Cerling et al. 1997, Bedaso, Z. K. 2013). The Chorora formation, a fault along the Somali continent at the Mid Ethiopian Rift, that formed as the Danakil block separated from the north-eastern part of the formation around 9 million years ago, shows a more mixed C3/C4 dietary strategy (Bernor et al. 2004) and increasingly C4-dominated diets are seen at the Adu-Asa Formation where the coastal grasslands on the Danakil block were at 6.5-5.2 Ma, and the Sagantole formation to where Danakil had rotated by 4.6-4.2 Ma. At Aramis and later on Hadar, the Danakil equid lineage had adapted as pure grazers. (White et al. 2009)

Synapses

Baskin, J., & Baskin, C. (1978). A Discussion of the Growth and Competitive Ability of C3 and C4 Plants. Castanea, 43(2), 71-76. Retrieved from http://www.jstor.org/stable/4032752

Jacobs, B. F., Kingston, J. D., & Jacobs, L. L. (1999). The Origin of Grass-Dominated Ecosystems. Annals of the Missouri Botanical Garden, 86(2), 590. https://doi.org/10.2307/2666186

Osborne, C. P., & Beerling, D. J. (2006). Nature’s green revolution: the remarkable evolutionary rise of C4 plants. Philosophical Transactions of the Royal Society B: Biological Sciences, 361(1465), 173–194. https://doi.org/10.1098/rstb.2005.1737

Janis, C. (2008). An Evolutionary History of Browsing and Grazing Ungulates. In Ecological Studies (pp. 21–45). Springer Berlin Heidelberg. https://doi.org/10.1007/978-3-540-72422-3_2

Cerling, T. E., Harris, J. M., MacFadden, B. J., Leakey, M. G., Quade, J., Eisenmann, V., & Ehleringer, J. R. (1997). Global vegetation change through the Miocene/Pliocene boundary. Nature, 389(6647), 153–158. https://doi.org/10.1038/38229

Bedaso, Z. K., Wynn, J. G., Alemseged, Z., & Geraads, D. (2013). Dietary and paleoenvironmental reconstruction using stable isotopes of herbivore tooth enamel from middle Pliocene Dikika, Ethiopia: Implication for Australopithecus afarensis habitat and food resources. Journal of Human Evolution, 64(1), 21–38. https://doi.org/10.1016/j.jhevol.2012.05.015

Bernor, R.L., Kaiser, T.M., Nelson, S.V., 2004. The oldest Ethiopian Hipparion (Equinae,
Perissodactyla) from Chorora. Systematics, paleodiet and paleoclimate.
Cour. Forsch-Inst. Senckenberg 246, 213e226.

White, T. D., Ambrose, S. H., Suwa, G., Su, D. F., DeGusta, D., Bernor, R. L., … Vrba, E. (2009). Macrovertebrate Paleontology and the Pliocene Habitat of Ardipithecus ramidus. Science, 326(5949), 67–67, 87–93. https://doi.org/10.1126/science.1175822

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