Unicellular eukaryotes, or protists, are among the most ancient organisms on Earth. Protists belong to multiple taxonomic groups; they are widely distributed geographically and in all environments. Their ability to discriminate among con- and heterospecifics has been documented during the past decade. Here we discuss exemplar cases of taxa-, clone-, and possible kin-discrimination in five major lineages: Mycetozoa (Dictyostelium, Polysphondylium), Dikarya (Saccharomyces), Ciliophora (Tetrahymena), Apicomplexa (Plasmodium) and Archamoebae (Entamoeba). We summarize the proposed genetic mechanisms involved in discrimination-mediated aggregation (self versus different), including the csA, FLO and trg (formerly lag) genes, and the Proliferation Activation Factors (PAFs), which facilitate clustering in some protistan taxa. We caution about the experimental challenges intrinsic to studying recognition in protists, and highlight the opportunities for exploring the ecology and evolution of complex forms of cell-cell communication, including social behavior, in a polyphyletic, still superficially understood group of organisms. Because unicellular eukaryotes are the evolutionary precursors of multicellular life, we infer that their mechanisms of taxa-, clone-, and possible kin-discrimination gave origin to the complex diversification and sophistication of traits associated with species and kin recognition in plants, fungi, invertebrates and vertebrates.

Persistent difficulties in resolving clear lineages in diverging populations of prokaryotes or unicellular eukaryotes (protistan polyphyletic groups) are challenging the classical species concept. Although multiple integrated approaches would render holistic taxonomies, most phylogenetic studies are still based on single-gene or morphological traits. Such methodologies conceal natural lineages, which are considered ‘cryptic’. The concept of species is considered artificial and inadequate to define natural populations. Social organisms display differential behaviors toward kin than to non-related individuals. In ‘social’ microbes, kin discrimination has been used to help resolve crypticity. Aggregative behavior could be explored in a non-social protist to define phylogenetic varieties that are considered ‘cryptic’. Two Entamoeba invadens strains, VK-1:NS and IP-1 are considered close populations of the same ‘species’. This study demonstrates that VK-1:NS and IP-1 trophozoites aggregate only with alike members and discriminate individuals from different strains based on behavioral and chemical signals. Combined morphological, behavioral/chemical and ecological studies could improve Archamoebae phylogenies and define cryptic varieties. Evolutionary processes in which selection acted continuously and cumulatively on ancestors of Entamoeba populations gave rise to behavioral and chemical signals that allowed individuals to discriminate non-population members and gradually, to new lineages; alternative views that claim a ‘Designer’ or ‘Creator’ as responsible for protistan diversity are unfounded.

Studies on clone- and kin-discrimination in protists have proliferated during the past decade. We report clone-recognition experiments in seven Entamoeba lineages (E. invadens IP-1, E. invadens VK-1:NS, E. terrapinae, E. moshkovskii Laredo, E. moshkovskii Snake, E. histolytica HM-1:IMSS and E. dispar). First, we characterized morphometrically each clone (length, width, and cell-surface area) and documented how they differed statistically from one another (as per single-variable or canonical-discriminant analyses). Second, we demonstrated that amebas themselves could discriminate self (clone) from different (themselves versus other clones). In mix-cell-line cultures between closely-related (E. invadens IP-1 versus E. invadens VK-1:NS) or distant-phylogenetic clones (E. terrapinae versus E. moshkovskii Laredo), amebas consistently aggregated with same-clone members. Third, we identified six putative cell-signals secreted by the amebas (RasGap/Ankyrin, coronin-WD40, actin, protein kinases, heat shock 70, and ubiquitin) and which known functions in Entamoeba spp. included: cell proliferation, cell adhesion, cell movement, and stress-induced encystation. To our knowledge, this is the first multi-clone characterization of Entamoeba spp. morphometrics, aggregative behavior, and cell-signaling secretion in the context of clone-recognition. Protists allow us to study cell-cell recognition from ecological and evolutionary perspectives. Modern protistan lineages can be central to studies about the origins and evolution of multicellularity.

The controversy evolution vs. creationism is inherent to the incompatibility between scientific rationalism/empiricism and the belief in supernatural causation. To test this hypothesis, we conceptualized a Cartesian landscape where the dependent variable acceptance of evolution was plotted as function of three factors, each represented by an index (value range 0 to 3): Religiosity Index (RI), Science Index (SI), and Evolution Index (EI). The indexes summarized an individual's personal religious convictions, familiarity with the processes and forces of change in organisms (= concept of evolution), and understanding the essence of science (= method to explore reality). We compared and contrasted acceptance of evolution among four populations of variable educational attainment: 244 professors of New England, United States (93% Ph.D./doctorate holders), 50 protistologists from 25 countries (70% Ph.D./doctorate holders), 62 educators of prospective teachers (83% Ph.D./doctorate holders), and 827 college students. The New England faculty held the highest acceptance of evolution position (RI = 0.49; SI = 2.49; EI = 2.49), followed by the protistologists (RI = 0.46; SI = 2.30; EI = 2.48), the educators of prospective teachers (RI = 0.83; SI = 1.96; EI = 1.96), and the students (RI = 0.89; SI = 1.80; EI = 1.60); therefore, the data supported our hypothesis. Proper science education, public outreach and robust debate over the controversy “evolution versus creationism” should suffice to improve society's evolution literacy, and qualified scholars ought to lead this mission.

Acceptance of evolution by educators of prospective teachers remains superficially studied despite their role in having mentored schoolteachers whose weak support of evolution is known. Here, we contrast the views of New England educators of prospective teachers (n=62; 87% Ph. D./doctorate holders in 32 specializations) with those of the general faculty (n=244; 93% Ph.D./doctorate holders in 40 disciplines), both members of 35 colleges and universities, and with college students (n=827; subsample of the 35 institutions) who were polled on: (1) the controversy evolution vs. creationism vs. intelligent design (ID), (2) their understanding of how science/evolution works, and (3) their religiosity. The educators held intermediate positions in respect to the general faculty and the students: 94% of the general faculty, 75% of the educators, and 63% of the students said they accepted evolution openly; and 82% of the general faculty, 71% of the educators, and 58% of the students thought that evolution is definitely true. Only 3% of the general faculty in comparison to 19% of the educators and 24% of the students thought that evolution and creationism are in harmony. Although 93% of the general faculty, educators, and students knew that evolution relies on common ancestry, 26% of the general faculty, 45% of the educators, and 35% of the students did not know that humans are apes. Remarkably, 15% of the general faculty, 32% of the educators, and 35% of the students believed, incorrectly, that the origin of the human mind cannot be explained by evolution; and 30% of the general faculty, 59% of the educators, and 75% of the students were Lamarckian (=believed in inheritance of acquired traits). For science education: 96% of the general faculty, 86% of the educators, and 71% of the students supported the exclusive teaching of evolution, while 4% of the general faculty, 14% of the educators, and 29% of the students favored equal time to evolution, creationism and ID; note that 92% of the general faculty, 82% of the educators, and 50% of the students perceived ID as either not scientific and proposed to counter evolution based on false claims or as religious doctrine consistent with creationism. The general faculty was the most knowledgeable about science/evolution and the least religious (science index, SI=2.49; evolution index, EI= 2.49; and religiosity index, RI=0.49); the educators reached lower science/evolution but higher religiosity indexes than the general faculty (SI=1.96, EI=1.96, and RI=0.83); and the students were the least knowledgeable about science/ evolution and the most religious (SI=1.80, EI=1.60, and RI=0.89). Understanding of science and evolution were inversely correlated with level of religiosity, and understanding of evolution increased with increasing science literacy. Interestingly, ≈36% of the general faculty, educators and students considered religion to be very important in their lives, and 17% of the general faculty, 34% of the educators, and 28% of the students said they prayed daily. Assessing t...