What Is Darwin's Theory Of Universal Common Ancestry?

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1. The objections to evolution by many non-scientists are mostly made without any previous research or investigations. It is argued that Darwin’s theory of evolution by common descent with modification does not support all living things. However, this theory is supported by many observations. Through geographic distribution, fossil records, morphology, embryology, and genomic analysis, evolution can be traced back to a common ancestry of living things. The development of phylogenies, relationships among species, and homologies, structural similarities between species, provide even more evidence to support common ancestry.
One of the biggest advances has come from molecular analysis of common ancestry. Compiling molecular phylogenies that focus
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2015. Life in the aftermath of mass extinctions. Curr Biol. 25(19): R941-R952.
Theobald DL. 2010. A formal test of the theory of universal common ancestry. Nature. 465(7295): 219-222.

2. There are many circumstances when deleterious alleles can persist in a population. Two of the reasons that this occurs are due to inbreeding, a type of non-random mating, and asexual reproduction. When inbreeding occurs, the frequency of homozygotes in a population increases. One of the negative circumstances that is associated with the increase in homozygosity is inbreeding depression. Inbreeding leads to a reduction in fitness of the population due to the homozygosity of deleterious alleles of offspring. These deleterious alleles are able to persist in these populations because there are no new alleles entering the population. Inbreeding causes a steady decline in population fitness since the deleterious alleles with move towards fixation. The homozygosity for these deleterious alleles will ultimate result in extinctions of small populations, especially if the reproduction rate in low (Wang et al. 1999). In one study, the effect of deleterious alleles on an inbreeding population of snakes was
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With a small population and disproportionate male reproductive success, inbreeding was the only method of reproduction. When this inbreeding population was compared with non-isolated populations of Vipera berus, the inbreeding population smaller litter sizes, a higher number of deformed and stillborn offspring and a limited amount of heterozygous individuals due to the fixation of alleles. This all led to a much higher amount of genetic similarity within the population. Once, males from other populations were introduced to the isolated population, the occurrences of deformations and inviable offspring was greatly reduced. Due to that discovery, the initial results show that the low reproduction rate and viability of Vipera berus in the isolated population result was a direct result of a persistence of deleterious alleles from inbreeding depression (Madsen et al. 1996). This is just one of many inbreeding populations that struggle to persist due to inbreeding
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