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Uric acid (UA) is the end product of purine metabolism in humans due to the loss of uricase activity by various mutations of its gene during the Miocene epoch, which led to humans having higher UA levels than other mammals. Furthermore, 90% of UA filtered by the kidneys is reabsorbed, instead of being excreted. These facts suggest that evolution and physiology have not treated UA as a harmful waste product, but as something beneficial that has to be kept. This has led various researchers to think about the possible evolutionary advantages of the loss of uricase and the subsequent increase in UA levels. It has been argued that due to the powerful antioxidant activity of UA, the evolutionary benefit could be the increased life expectancy of hominids. For other authors, the loss of uricase and the increase in UA could be a mechanism to maintain blood pressure in times of very low salt ingestion. The oldest hypothesis associates the increase in UA with higher intelligence in humans. Finally, UA has protective effects against several neurodegenerative diseases, suggesting it could have interesting actions on neuronal development and function. These hypotheses are discussed from an evolutionary perspective and their clinical significance. UA has some obvious harmful effects, and some, not so well-known, beneficial effects as an antioxidant and neuroprotector. [ABSTRACT FROM PUBLISHER]

One of the classic examples of faunal turnover in the fossil record is the Miocene transition from faunas dominated by anchitheriine horses with low-crowned molar teeth to faunas with hipparionine horses characterized by high-crowned teeth. The spread of hipparionine horses is associated with increased seasonality and the expansion of open habitats. It is generally accepted that anchitheriine horses did not display an evolutionary increase in tooth crown height prior to their extinction. Nevertheless, to test whether anchitheriines showed any changes interpretable as adaptation to local conditions, we analyzed molar teeth from multiple populations of Anchitherium in three dimensions. Our results show differences in tooth morphology that suggest incipient hypsodonty in Spain, the first region experiencing increasingly arid conditions in the early Miocene of Europe. Furthermore, analyses of tooth wear show that Spanish specimens cluster with present ungulates that eat foliage together with grasses and shrubs, whereas German specimens cluster with present-day ungulates that eat mostly foliage. Taken together, even a taxon such as Anchitherium, with a long and successful history of forest adaptation, did respond to regional environmental changes in an adaptive manner. [ABSTRACT FROM AUTHOR]

Carnivores are ecologically diverse mammals. Dietary adaptations vary from strict herbivory to pure carnivory. These adaptations have evolved independently several times within families, so evolution within the order is iterative. I used 2 databases to examine whether ecological adaptations have an effect on longevity or spatial distributions of fossil carnivores. Miocene hypercarnivorous species had, on average, the widest spatial distributions. Their temporal distributions were not significantly longer than those of other carnivores. Body size also had a significant interaction with maximum spatial distribution. Largebodied carnivores, regardless of feeding adaptations, had larger geographical ranges, but did not have greater longevity. However, when all the data were pooled, temporal distribution had a significant correlation with spatial distribution. The position of hypercarnivores at the top of the food chain and their specialized adaptations for meat eating probably increased their extinction risk to the same level of more narrowly distributed, less specialized carnivores. [ABSTRACT FROM AUTHOR]