Biological proxies

Foster, M.W. and R.R. Sharp, "Race, Ethnicity, and Genomics Social Classifications as Proxies of Biological Heterogeneity," Genome Res., 12, 844-850 (2002). 

Reproductive success measured where there is effective contraception is, of course, of limited value in assessing the evolutionary utility of a given human behavior. Under these modem conditions it may be better to measure mate value, i.e., sexual attractiveness, as a proxy for reproductive success (e.g., Dong et al., 1996 Weisfeld et al., 1992). Sexual attractiveness, of course, refers to an emotion and as such is a proximate cause of ultimate biological success. 

First, the temperature changes. The mean environmental temperature is readily accessible, but data for the past are to be taken with prudence since the measurement of temperature is a recent acquisition. Indirect evidence (Fig. 16.2.3.1) suggests that the Little Ice Age, which lasted from the end of the Middle Ages until the mid 19 century, was colder than now (0.5 C). Such conclusions derive mainly from the analysis of proxies, which are geographically scattered indicators, in the form of both natural (physical and biological) and documentary (written) archives for the last millenniiun... 

Potential interfering substances in a biological matrix include endogenous matrix components, metabolites, decomposition products, and in the actual study, concomitant medication. Whenever possible, the same biological matrix as the matrix in the intended samples should be used for validation purposes. For tissues of limited availability, such as bone marrow, physiologically appropriate proxy matrices can be substituted. Method selectivity should be evaluated during method development and method validation and can continue during the analysis of actual study samples. 

Limited Quantity of Matrices. For biological matrices that are difficult to obtain, only a single source may be available and is therefore the only possibility for testing selectivity. These matrices include, but are not limited to, human and primate tissue and cerebrospinal fluid. In the absence of the corrected biological matrix, as the 2000 Washington conference final report suggests, a physiologically appropriate proxy matrix can be used. 

In this chapter, we discuss paleoaltimetric application of stable isotopes in fossils. Fossils share some features of other stable isotope proxies, for example in their link to atmospheric circulation patterns and meteoric water compositions. However they differ in other key respects, for example in their link to biology, and in their preservation of seasonal isotope variations, reflecting seasonal climate. These variations complicate some interpretations, but also provide alternative approaches to constrain elevations. 

There are two main types of geochemical proxy used to identify former life. These are biomarker molecules and isotopic fractionations. Biomarker molecules are specific molecules preserved in sediments as molecular fossils, which are unambiguous indicators of their biological precursors. Some of the most successful... 

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