Fossil Sheds Light on Early Primates

The ancient remains of a tiny primate suggest it likely ate insects, lived in trees, and weighed less than an ounce.

By | June 6, 2013

An artistic rendering of Archicebus achillesXIIJUN NI, INSTITUTE OF VERTEBRATE PALEONTOLOGY AND PALEOANTHROPOLOGY, CHINESE ACADEMY OF SCIENCESA 55 million-year-old primate fossil called Archicebus achilles, unearthed in China in 2002, is an early ancestor of the modern tarsier, according to an analysis published in Nature this week (June 4). The oldest complete primate fossil yet found, it gives clues into what early primates looked like.

Modern tarsiers are tree-dwelling primates that live on Southeast Asian islands. The tarsier lineage split off from the anthropoids, the lineage that gave rise to monkeys, apes, and humans, just slightly before the time of the fossil specimen, the authors suggest.

Therefore the physical features of the fossil likely are representative of what the common ancestor of tarsiers and humans may have looked like, according to a Nature news article. The fossil primate’s tooth shapes indicate a diet of insects. Its small eye sockets suggest that the ancient primates were diurnal, unlike tarsiers, which have since evolved larger eyes to better see in the dark. The fossil’s long tail and hind limbs would have been well suited for living in trees.

The fossil also bolsters the theory that primates evolved in Asia and only later migrated to Africa, according to ScienceNOW.

“You don’t get these kinds of complete fossils very often,” John Fleagle, a paleontologist at Stony Brook University who was not involved in the study, told ScienceNOW. “It documents an aspect of primate evolution that we didn’t have much documentation for.”

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Avatar of: James V. Kohl

James V. Kohl

Posts: 492

June 8, 2013

Part 1: See Kamberov et al. (2013) and Grossman et al (2013): The fossil location suggest that  a climate change-dependent diet-dependent amino acid substitution led to culture-driven sexual selection for pheromones associated with visually perceived phenotype in a human population that arose in central China during the past ~30,000 years. Perhaps the timing of the climate change et al. is coincidental. However, their findings of epigenetic cause and effect conflict with mutations theory and the 55 million years time frame due to the fact that olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans.

For example, single amino acid substitutions result in species diversification in a variety of accepted animal models best exemplified in insects. Perhaps this insectivore primate's adaptive evolution was nutrient-dependent and pheromone-controlled as is adaptive evolution in every other species on this planet. If so, it may not have taken 55 million years to evolve via ecological, social, neurogenic, and socio-cognitive niche construction and become a modern human. It seems more likely to me that the epigenetic tweaking of a few genes with large effects might have sped things up. Why wait for random mutations to somehow accumulate and cause something, when there is no evidence to suggest that random mutations cause adaptive evolution?

Besides, the idea that other primates first evolved in Asia fits nicely with what Darwin told us about the 'conditions of life' required before natural selection and natural cooperation could proceed. Darwin's 'conditions of life' are, of course, nutrient-dependent and pheromone-controlled.

See: Kohl, J.V. (2012) Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338. DOI: 10.3402/snp.v2i0.17338.

Part 2: After reading the article in Nature, I think it is even more important to consider the context of nutrient-dependent pheromone-controlled morphogenesis of the teeth (e.g., in what may be the last common ancestor of all primates with their origins in what is now central China). It's unlikely that the teeth of this insectivore adaptively evolved via epigenetic effects of visual input associated with ingestive behavior. However, epigenetic effects of nutrient acquisition on morphogenesis extend across species.

In my model, the epigenetic effects of nutrient acquisition on morphogenesis are constrained by the metabolism of nutrients to species-specific pheromones that control reproduction in species from microbes to man. We could use that model to begin to evaluate the time required for the number of polymorphisms and genes of large effect to result in Neanderthal to 'modern human' adaptive evolution.

An evidence-based approach to establishing constraints on mutations could then include 'Analysis of 6,515 exomes [that] reveals the recent origin of most human protein-coding variants' (Fu et al, 2013). Mutations of large effect seem to have occurred during the past 5-10,000 years. This suggests that, with few exceptions, the beneficial mutations are actually nutrient-dependent pheromone-controlled adaptations. Doesn't it?

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