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Introduction

Phylogenetics refers to the study of evolutionary associations which involve diverse groups or class of organisms. Such evolutionary relationships are discovered by means of molecular statistics and morphological data matrices. The term phylogenetics is a self descriptive term of Greek origin which means "tribe, or race related by birth". Identification, classification, and naming of organisms have been opulently informed by phylogenetics. Moreover, it relates to other biological disciplines in a number of ways, for instance, it overlaps with taxonomy in the science of Phylogenetic Systematic. According to Larget & Simon (1999, 12-17), Phylogenetic Analysis, especially with its interaction with other disciplines, has become an essential feature in establishing the evolutionary tree of life. In this regard, to better understand Phylogenetic Reconstruction, a brief history of the mammalian evolutionary process would be essential.

The evolution of mammals throughout history was a gradual process stretching approximately fifty million years, between 280 and 230 million years ago (the Permian Period). Furthermore, between 230 million years ago and 190 million years ago (Triassic Period), many organisms which resembled mammals came into existence. These organisms were not biologically mammals as they lacked some of the mammalian characteristics. Nonetheless, they were considered as the antecedents of mammals. It was not until the Jurassic Period (190 and 135 million years ago) that the first true mammals appeared.  The Jurassic Period was also marked by great evolutionary transformations, key among them being the end of ancient reptiles as well as the appearance of flowering plants and modern insects (Murphy et al, 45).

The earliest mammals, that is the eutherian and pouched mammals acquired new life forms and established biological environments through which all modern mammals have appeared. Since their appearance, many other mammals have emerged with more or less similar characteristics. In this regard, in a bid to examine the mammalian evolution, researchers have employed a number of phylogenetic techniques which are exemplified by: Maximum Parsimony; Minimum Evolution; Maximum Likelihood and Bayesian Analyses. In this study, we shall be confined to a literary review of Maximum Parsimony and Minimum Evolution while pointing out their strengths and weaknesses.