We explore the evidential relationships that connect two standard claims of modern evolutionary biology. The hypothesis of common ancestry (which says that all organisms now on earth trace back to a single progenitor) and the hypothesis of natural selection (which says that natural selection has been an important influence on the traits exhibited by organisms) are logically independent; however, this leaves open whether testing one requires assumptions about the status of the other. Darwin noted that an extreme version of (...) adaptationism would undercut the possibility of making inferences about common ancestry. Here we develop a converse claim—hypotheses that assert that natural selection has been an important influence on trait values are untestable unless supplemented by suitable background assumptions. The fact of common ancestry and a claim about quantitative genetics together suffice to render such hypotheses testable. Furthermore, we see no plausible alternative to these assumptions; we hypothesize that they are necessary as well as sufficient for adaptive hypotheses to be tested. This point has important implications for biological practice, since biologists standardly assume that adaptive hypotheses predict trait associations among tip species. Another consequence is that adaptive hypotheses cannot be confirmed or disconfirmed by a trait value that is universal within a single species, if that trait value deviates even slightly from the optimum. 1 Two Darwinian hypotheses 2 Logical independence 3 How adaptive hypotheses bear on the tree of life hypothesis 4 How the tree of life hypothesis bears on adaptive hypotheses 5 What do adaptive hypotheses predict? 6 Common ancestry and quantitative genetics to the rescue 7 Conclusion. (shrink)

This paper is an attempt to identify common factors which constitute the foundation of decolonization in indigenous African religions. Since such aspects need to be essentially constructive in order to effectively and positively replace Colonial ideas, this particular search for common ground concerning decolonization in indigenous African religions is going to be pursued through the concept of ecodomy, seen as constructive process. When applied to decolonization with this postulated positivity, ecodomy coagulates three distinct aspects of indigenous African religions into a (...) common reality. These three aspects are ancestry, goodness, and the relationship with Christianity; they can function therefore as common denominator for various attempts to provide indigenous African religions with specific methodology in dealing with decolonization. This article is going to investigate four such methodologies which can confer positivity as well as an ecodomic, constructive character to decolonization efforts throughout the spectrum of indigenous African religions as they are reflected in the writings of John Mbiti, Isiaka P. Lalèyê, Jakob K. Olupona, and Israel Kamudzandu, all intellectuals of different geographical origin, religious backgrounds, university training, and personal convictions. With Mbiti promoting the superiority of Christianity, Lalèyê accepting it as irrelevant, Olupona preferring to deal without it, and Kamudzandu seeing it as essential, decolonizing efforts in indigenous African religions have at least four different methodologies which all aim at providing African communities with positive and ecodomic, essentially constructive ways to move forward beyond Colonial intellectual paradigms by making sure that peace and goodness are secured for everybody, African or not. (shrink)

The environmental complexity in which living organisms found themselves throughout evolution, most likely resulted in various encounters that would continuously challenge the organisms' ability to survive. Coping with this stress can prove energetically demanding and might require the proper coupling between mechanisms aimed at sensing external stimuli and cellular strategies geared at producing energy. In this issue of BioEssays, Lovejoy and Hogg hypothesize that preservation of this bifaceted coupling can be detected by the maintenance and evolution of stress response mechanisms (...) at the genomic, molecular and cellular levels. Through ancestry‐tracking, they identify a group of related G protein‐coupled receptor systems with intersecting stress‐modulating properties which might represent an essential part of a complex organism's coping mechanisms to stress, an attribute that they suspect may be affected in individuals suffering from mood disorders such as depression. (shrink)

This paper is an attempt to offer a concrete contribution to the study of indigenous African religions and in particular to the support of creating a set of traditions from whose perspective one could engage in the study of indigenous African religions as well as of African spirituality in general through the unifying theme of ecodomy. Defined in terms of a constructive process, ecodomy seeks to provide families and communities with a common element, that of ancestors, which is not only (...) specific to African spirituality but also potentially capable of strengthening and improving the life of African people. Thus, this methodology based on working with ancestry as economy is applied to four distinct scholars and their specific approaches to indigenous African religions: John S. Mbiti, who believes that ancestors have mainly social, not religious roles; Issiaka P. Laleye, for whom ancestors make a connection between the social and religious aspects of life; Jacob K. Olupona, who restricts ancestors to religion, and Israel Kamudzandu, in whose philosophy ancestors can provide African societies with the possibility of moving beyond their indigenous religions into accepting other religious beliefs, such as those provided by Christianity. (shrink)

ABSTRACTAs both a geneticist and a Nigerian living in the United States, the author responds to the prospect of African Americans using genetic science to trace their ancestry to the African continent. He articulates concerns about both the limitations of the science to offer satisfying, accurate, and meaningful results, and the ability of individuals to make real, life‐altering sense of these results. However, he notes that given the history and impact of slavery on African Americans, the desire to trace (...) roots to Africa is both real and understandable. (shrink)

Suetonius’ Lives of the Caesars usually begin with a family tree. These family trees are often rhetorical, foreshadowing in the ancestors character traits that will be themes of the rest of the Life. This particular rhetorical strategy relies upon an older phenomenon of ‘family identity’—namely, the literary application of similar characteristics to people in the same family—such as the one that tells us that the Claudii are proud and the Domitii Ahenobarbi are ferocious. Gary Farney studied ‘family identity’ as a (...) phenomenon of the Republic. There, it was the association of a family with a certain characteristic, a kind of ‘branding’. It would be perfectly obvious for Suetonius to use the family identities already in use for well-known families, but, as I show here, Suetonius’ selection of ancestors creates different family identities rather than simply using the traditional ones he would have found in other sources. In this study I concentrate on Nero and Tiberius. I focus on these two emperors because they are individuals where there is a known family identity in other sources and they also have the most detailed and elaborate ancestry sections in Suetonius’ Caesars. Family identity seems to be most interesting to Suetonius when it goes against expectations, and that is when Suetonius’ family trees are most elaborate. (shrink)

The third stasimon of Oedipus Rex is the climax of the play, separating the conversation with the Corinthian messenger from the interrogation of the shepherd, so crucial for the narrative. Indeed, the question τίς σε, τέκνον, τίς σ’ ἔτικτε, critical for the plot, comes right at the beginning of its antistrophe. Sophocles, however, offers no easy answer to it. Instead, he provides yet another narrative misdirection, one that—for the last time—suggests that the paths of the king of Thebes and of (...) his predecessor may have been divergent: the possibility that Oedipus’ divine ancestry would question the prophecy of Apollo. After enumerating Pan, Hermes and Apollo himself as possible parents, the song also mentions Dionysus and the ‘Heliconian nymphs’. The reference to Helicon has perplexed the readers for many years, since the text seems to focus on Cithaeron as the ‘birthplace’. As a result, editions and translations prefer the conjecture ἑλικωπίδων proposed by U. von Wilamowitz-Moellendorff in 1879, over Ἑλικωνίδων, the form present in all manuscripts. In this paper I argue that an analysis of our sources for Heliconian cults, an assessment of the performative context, and a close reading of the stasimon and its place in the narrative, all suggest that the manuscript reading should be retained. (shrink)

The ABO histo‐blood group, first discovered over a century ago, is found not only in humans but also in many other primate species, with the same genetic variants maintained for at least 20 million years. Polymorphisms in ABO have been associated with susceptibility to a large number of human diseases, from gastric cancers to immune or artery diseases, but the adaptive phenotypes to which the polymorphism contributes remain unclear. We suggest that variation in ABO has been maintained by frequency‐dependent or (...) fluctuating selection pressures, potentially arising from co‐evolution with gut pathogens. We further hypothesize that the histo‐blood group labels A, B, AB, and O do not offer a full description of variants maintained by natural selection, implying that there are unrecognized, functionally important, antigens beyond the ABO group in humans and other primates. (shrink)

BackgroundGenealogical research and ancestry testing are popular recreational activities but little is known about the impact of the use of these services on clients’ biological and social families. Ancestry databases are being enriched with self-reported data and data from deoxyribonucleic acid analyses, but also are being linked to other direct-to-consumer genetic testing and research databases. As both family history data and DNA can provide information on more than just the individual, we asked whether companies, as a part of (...) the consent process, were informing clients, and through them clients’ relatives, of the potential implications of the use and linkage of their personal data.MethodsWe used content analysis to analyse publically-available consent and informational materials provided to potential clients of ancestry and direct-to-consumer genetic testing companies to determine what consent is required, what risks associated with participation were highlighted, and whether the consent or notification of third parties was suggested or required.ResultsWe identified four categories of companies providing: 1) services based only on self-reported data, such as personal or family history; 2) services based only on DNA provided by the client; 3) services using both; and 4) services using both that also have a research component. The amount of information provided on the potential issues varied significantly across the categories of companies. ‘Traditional’ ancestry companies showed the greatest awareness of the implications for family members, while companies only asking for DNA focused solely on the client. While in some cases companies included text recommending clients inform their relatives, showing they recognised the issues, often it was located within lengthy terms and conditions or privacy statements that may not be read by potential clients.ConclusionsWe recommend that companies should make it clearer that clients should inform third parties about their plans to participate, that third parties’ data will be provided to companies, and that that data will be linked to other databases, thus raising privacy and issues on use of data. We also suggest investigating whether a ‘generational consent’ should be created that would include more than just the individual in decisions about participating in genetic investigations. (shrink)

Common ancestry is a central feature of the theory of evolution, yet it is not clear what “common ancestry” actually means; nor is it clear how it is related to other terms such as “the Tree of Life” and “the last universal common ancestor”. I argue these terms describe three distinct hypotheses ordered in a logical way: that there is a Tree of Life is a claim about the pattern of evolutionary history, that there is a last universal (...) common ancestor is an ontological claim about the existence of an entity of a specific kind, and that there is universal common ancestry is a claim about a causal pattern in the history of life. With these generalizations in mind, I argue that the existence of a Tree of Life entails a last universal common ancestor, which would entail universal common ancestry, but neither of the converse entailments hold. This allows us to make sense of the debates surrounding the Tree, as well as our lack of knowledge about the last universal common ancestor, while still maintaining the uncontroversial truth of universal common ancestry. (shrink)

It will be noticed that, in the stemma above, no line of descent is marked from the first generation registered therein to the following generations. The genealogy of the Emperor Nerva is customarily traced back to the consul of 36 b.c., M. Cocceius Nerva. This short note will underline the ancient testimony found amongst the Pseudacroniana tracing his descent from the latter's brother, the consummate diplomat. There are ramifications. Amongst the items of interest will be the light shone upon what (...) Dio and Eutropius understood to be Nerva's standing at the time of his accession. Before passing on to Pseudacron's datum, it might be worthwhile pausing on that point, as well as briefly contemplating the factors that actually bore upon the emperor's ancestral training. (shrink)

In the Severan period the proconsulship of Africa or Asia was normally held some 15 to 17 years after die consulship. Although there are comparatively few consuls in this period whose ages can be firmly established, what evidencethere is suggests that the consulship was normally held in the early forties, on occasions as early as the mid thirties: a consularis could, therefore, hope to attain a premier proconsulship aged about 60. Thus the future emperor P.Helvius Pertinax, who was born on (...) 1st August 126, held the proconsulship of Africa, probably in 188/9, at the age of 62. M. Didius Julianus, the imperial successor to Pertinax, also succeeded him in Africa aged about 56. C. Vettius Sabinianus was born before 136 and his proconsulship fell about 192/37 whenhe was at least 56 years old. (shrink)

In Democracy and Education, in the midst of the pivotal chapter on “The Democratic Conception in Education,” Dewey juxtaposes his educational aims with those of Plato, Rousseau, Fichte and Hegel. Perhaps Dewey believed that an account of their views would help elucidate his own, or he intended to suggest that his own ideas rivaled or bested theirs. I argue that Dewey’s discussion of historical philosophers’ aims of education was also designed to critique his contemporaries subtly and by analogy. My analysis (...) of Dewey’s critique supports a second argument: one of the reasons Dewey’s legacy has been long debated (particularly his relationship to pedagogical progressivism) derives from his reluctance to criticize his contemporaries explicitly and directly. Had Dewey critiqued his fellow American progressives in the same way he did historical European philosophers of the past, his readers would have better understood his relationship to progressive American educational ideas and practices. Yet Dewey’s subtle approach also accounts for the creation of a work that genuinely warrants being called a classic – it rises above the educational debates of the early twentieth century to enter into a conversation with its educational ancestry, a conversation that Dewey propelled forward. (shrink)

This article contributes to discussions of methodology in gender studies by examining narrative analysis as a feminist method. Using direct-to-consumer genetic ancestry services as a case study, the author discusses the potential of narrative analysis in interrogating complex cultural phenomena. The analysis focuses on the commercial website of the UK-based genetics company Oxford Ancestors, which the author situates at the intersection of the cultural narratives of commercialization, scientific advance and personal quest. By interrogating the mutual embeddedness of these narratives, (...) the author demonstrates how narrative analysis moves across structure and context capturing the processes through which facts about gender come into being. The author suggests that this focus on the tension between the abstract and the specific in cultural phenomena is what makes narrative analysis a particularly effective tool for feminist cultural analysis. (shrink)

This article examines a genetic ancestry testing program called the Living History Project that was jointly organized by a nonprofit educational institute and a for-profit genealogy company in South Africa. It charts the precise mechanisms by which the LHP sought to shape a postapartheid genome through antiracist commitments aimed at contesting histories of colonial and apartheid rule in varied ways. In particular, it focuses on several tensions that emerged within three modes of material-discursive practice within the production of the (...) LHP: subject recruitment, informed consent, and participant reflections. In the end, it argues that several contradictory tensions were central to the making of the LHP’s postapartheid genome and that it should be understood as nonracial rather than antiracist. (shrink)

By inferences from fossil records and circumstantial evidences, it is now generally postulated that angiosperms have a much longer history than hitherto believed and that they have already existed probably in Jurassic time. Studies in vascular tissues and reproductive, structures have negated the possibility of originating angiosperms from various gymnosperm groups. Chronologically, this derivation will be also an impossibility.From a consideration of various aspects in the life history of angiosperms, a hypothesis is here presented postulating that protangiosperms originated in an (...) aquatic or subaquatic environment from an algal ancestry. The enclosure of ovules in the ovary is interpretated as a means of protection necessitated for the transmigration from an aquatic to an aerial habitat for the developing reproductive parts in the bud underwater. Trimery is suggested as a primitive condition, one that affords maximum efficiency in carrying out the purpose under the conditions.In the life history of angiosperms, the endosperm is of great significance in phylogeny. From morphological, physiological, cytological as well as genetical considerations, the endosperm should be regarded as of equal status with the gametophytic and sporophytic generations. There is no comparable structure in the gymnosperm groups and the ferns and “fern-allies”, while more or less similar conditions are present in the thallophytes. In the long life histories of many red algae, however, there is an especially notable resemblance to angiosperms, with certain details approaching the unique and characteristic features of the endosperms.Land plants are presumably all evolved from aquatic ancestors but instead of the usual concept of a monophyletic origin and lineal development of all vascular plants, a more plausible suggestion is the multiple and recurrent derivation of such plants from various algal ancestral groups. The angiosperms probably represent one of such major lines that originated more or less directly from a thallophytic ancestry. (shrink)

This article looks at the feminist activism of particular women in the ancestry of the eminent Canadian sociologist, Dorothy E. Smith, and at the archival data that confirm the traces of their influence found in her theory-building. Using the method of interpretative historical sociology and a conceptual framework drawn from Marx called the `productive forces', the article examines the feminist theology of her Quaker ancestor, Margaret Fell, and the militant suffrage activism of her mother and her grandmother, Dorothy Foster (...) Place and Lucy Ellison Abraham, respectively. The article argues that the household labour of the remarkable women in her family line became a `productive force' that facilitated her imagining of the feminist theory, `the standpoint of women'. (shrink)

Sociological accounts usually emphasise the primacy of phenotype (cor, colour) over ancestry for orienting concepts of ‘race’ in Brazil. In this paper, I present an alternative account of the cultural and political significance of ancestry in contemporary Brazil, drawing on qualitative interviews conducted with 50 Brazilians who had recently taken personalised DNA ancestry tests. The interviewees’ attitudes towards their ancestry are interpreted in relation to Brazil’s longstanding national myth of mestiçagem and the history of eugenic Whitening (...) ideologies (ideologias do branqueamento) that have sought to erase traces of Brazil’s African origins. However, they are also interpreted also against the backdrop of contemporary Black Movement activism that aims to actively recovering Afro-Brazilian histories and memories from these processes of erasure. (shrink)

I consider three theses that are friendly to anthropomorphism. Each makes a claim about what can be inferred about the mental life of chimpanzees from the fact that humans and chimpanzees both have behavioral trait B and humans produce this behavior by having mental trait M. The first thesis asserts that this fact makes it probable that chimpanzees have M. The second says that this fact provides strong evidence that chimpanzees have M. The third claims that the fact is evidence (...) that chimpanzees have M. The third thesis follows from a plausible Reichenbachian model of how a common ancestor is probabilistically related to its descendants. The first two theses do not, and they have no general evolutionary justification. (shrink)

Chance has been a focus of attention ever since the beginning of population genetics, but neutrality has not, as natural selection once appeared to be the only worthwhile issue. Neutral change became a major source of interest during the neutralist–selectionist debate, 1970–1980. It retained interest beyond this period for two reasons that contributed to its becoming foundational for evolutionary reasoning. On the one hand, neutral evolution was the first mathematical prediction to emerge from Mendelian inheritance: until then evolution by natural (...) selection was considered the alternative to the fixity of species; now it appears to be the alternative to continuous change. Second, neutral change generated a set of clear predictions on standing variation. These could be used as a reference for detecting more elusive alternative mechanisms of evolution including natural selection. In the wake of the transition from Mendelism to genomics, the combination of coalescent theory, DNA sequence variation, and numerical analysis made it possible to integrate contingent aspects of the history of species into a new null model, thus opening a new dimension in the concept of population that the Modern Synthesis formerly considered as a mere gene pool. (shrink)

Reid’s rejection of the “theory of ideas” implies that sensations are not copies of external qualities such as extension and figure. Reid also says that not even the order of sensations is spatial. However, in his early manuscripts Reid did not deny that sensations are arranged spatially. He simply denied that our ideas of extension and figure are copied from any single atomic sensation. Only subsequently did Reid explicitly reject the view that sensations are arranged spatially. The question of the (...) spatiality of color sensation was a central concern of early interpreters of Reid, like Dugald Stewart, John Fearn, and William Hamilton. In particular, John Fearn thought that the denial of the spatiality of color sensations is the result of Reid’s commitment to the immateriality of the soul. Against Reid’s view, Fearn argued that the perception of visible figure necessarily implies the spatiality of color sensations. (shrink)

ABSTRACT:A wide range of research uses patterns of genetic variation to infer genetic similarity between individuals, typically referred to as genetic ancestry. This research includes inference of human demographic history, understanding the genetic architecture of traits, and predicting disease risk. Researchers are not just structuring an intellectual inquiry when using genetic ancestry, they are also creating analytical frameworks with broader societal ramifications. This essay presents an ethics framework in the spirit of virtue ethics for these researchers: rather than (...) focus on rule following, the framework is designed to build researchers’ capacities to react to the ethical dimensions of their work. The authors identify one overarching principle of intellectual freedom and responsibility, noting that freedom in all its guises comes with responsibility, and they identify and define four principles that collectively uphold researchers’ intellectual responsibility: truthfulness, justice and fairness, anti-racism, and public beneficence. Researchers should bring their practices into alignment with these principles, and to aid this, the authors name three common ways research practices infringe these principles, suggest a step-by-step process for aligning research choices with the principles, provide rules of thumb for achieving alignment, and give a worked case. The essay concludes by identifying support needed by researchers to act in accord with the proposed framework. (shrink)

Name der Zeitschrift: Millennium Jahrgang: 11 Heft: 1 Seiten: 69-100.

A Teaching Memoir That Crosses the Barriers Between Worlds A shaman is one who has learned to move between two worlds: our physical reality and the realm of spirits. For John Lockley, shamanic training also meant learning to cross the immense divide of race and culture in South Africa. As a medic drafted into the South African military in 1990, John Lockley had a powerful dream. "Even though I am a white man of Irish and English descent, I knew in (...) my bones that I had received my calling to become a sangoma, a traditional South African shaman," John writes. "I felt blessed by the ancient spirit of Africa, and I knew that I had started on a journey filled with magic and danger." His path took him from the hills of South Korea, where he trained as a student under Zen Master Su Bong, to the rural African landscape of the Eastern Cape and the world of the sangoma mystic healers, where he found his teacher in the medicine woman called MaMngwevu. In Leopard Warrior, John shares a gripping account of his experiences and the wisdom he learned over years of training. Here he invites you to discover: • Powerful insights into the spiritual tradition of the Xhosa lineage of South Africa—the tribe of Nelson Mandela and Desmond Tutu • Ubuntu—a core concept for recognizing and embracing our deep interconnection with all living things • Ancestor medicine—how we can learn to honor the blood in our veins, the heritage of our soul, and our shared humanity • Recovering our forgotten knowledge about the wisdom of our dreams, the spirits of plants and animals, and the power of the unseen world In traditional African healing circles, the leopard represents intuition, instinct, and harmony with nature and the spirit world. As John Lockley writes, "A leopard warrior is a spiritual soldier who mirrors the natural world and directs their gaze inward to answer the call of their spirit." With Leopard Warrior, he brings us an inspiring call to action—showing how we can bridge the barriers that divide us, embrace the gifts of our ancestors, and reclaim our rightful place as compassionate caretakers of our world. (shrink)

En esta reseña crítica de Permanent Markers: Race, Ancestry, and the Body After the Genome, ofrezco una lectura íntima del análisis que la autora Sarah Abel hace de los usos de las pruebas de ancestría en Brasil y Estados Unidos. Destaco la contribución metodológica de libro (el análisis comparativo de dos contextos nacionales muy distintos) y enfatizo los hallazgos de la investigación en el contexto de una década de trabajos que se han ocupado también de los usos sociales de (...) las tecnologías del ADN y de las discusiones que estos usos suscitan en torno a la racialización de las identidades y el potencial antirracista de la ciencia genética. Finalmente, señalo una crítica menor referente a la aplicación forense de las pruebas genealógicas. Ello permite mostrar otras importantes avenidas de indagación que el libro suscita. (shrink)

Recent advances in population genetics have made it possible to infer an individual's ancestral origin with a high degree of reliability, giving rise to the new technology called ‘DNA Ancestry Profiling’. Bioethicists have raised concerns over using this technology within a forensic context, many of which stem from issues concerning race. In this article, I offer some reasons why we ought to allow forensic scientists to use DNA Ancestry Profiling to infer the race or ethnicity of perpetrators — (...) on a particular understanding of race or ethnicity — in at least some cases. First, there is reason to think the process will meet our evidential standards in many cases. Second, the technology has serious prospects for improving racial justice. Third, the ethical concerns that have been raised can be addressed. And last, using Forensic DNA Ancestry Profiling to infer race or ethnicity has many benefits over its successor technology known as Molecular Photofitting. I conclude the essay by sketching the empirical work that remains to be done. (shrink)

The growth of consumer DNA ancestry testing has resulted in questions and critiques being raised in social and research contexts. This study examined individuals discussing their ancestry DNA testing results on YouTube by searching for the two most popular testing companies (23andMe; Ancestry) and the phrase “DNA results.” The finalized dataset consisted of 117 videos, on which directed content analysis was performed. In the videos, individuals used results to clarify, confirm, question, and re-evaluate their previously held conceptions (...) of racial/ethnic identities. Reactions were more positive than negative (88.1% vs. 8.1%), and results more commonly reaffirmed (77.8%) than re-conceptualized (40.0%) one’s racial/ethnic identity. Ancestry testing and personal social media accounts were commonly promoted, demonstrating biotechnological hype where promotion abounds and critiques are scarce. Questions persist around the impact of ancestry DNA testing in reifying a scientifically inaccurate conception of race and what impact YouTube videos might have on audiences. (shrink)

ABSTRACT Darwin claims in the Origin that similarity is evidence for common ancestry, but that adaptive similarities are ‘almost valueless’ as evidence. This second claim seems reasonable for some adaptive similarities but not for others. Here we clarify and evaluate these and related matters by using the law of likelihood as an analytic tool and by considering mathematical models of three evolutionary processes: directional selection, stabilizing selection, and drift. Our results apply both to Darwin’s theory of evolution and to (...) modern evolutionary biology. _1_ Introduction _2_ The Likelihood Framework _3_ A Sufficient Condition for a Similarity to Favour Common Ancestry over Separate Ancestry _4_ The 1/p Criterion and Its Limitations _5_ Directional Selection versus Drift _6_ Stabilizing Selection versus Drift _7_ Going beyond Two Taxa _8_ Conclusions Appendix. (shrink)

Darwin claims in the Origin that similarity is evidence for common ancestry, but that adaptive similarities are ‘almost valueless’ as evidence. This second claim seems reasonable for some adaptive similarities but not for others. Here we clarify and evaluate these and related matters by using the law of likelihood as an analytic tool and by considering mathematical models of three evolutionary processes: directional selection, stabilizing selection, and drift. Our results apply both to Darwin’s theory of evolution and to modern (...) evolutionary biology. 1 Introduction2 The Likelihood Framework3 A Sufficient Condition for a Similarity to Favour Common Ancestry over Separate Ancestry4 The 1/p Criterion and Its Limitations5 Directional Selection versus Drift6 Stabilizing Selection versus Drift7 Going beyond Two Taxa8 ConclusionsAppendix. (shrink)