directional selection in the modern horse is demonstrated bydivinity 2 respec talents

. There are some animals, like Thalassocnus, that go through a very direct, linear evolutionary path with very few (if any) sidebranches. The domestication of the horse began about 5500 years ago in the Eurasian steppes. Article Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Directional evolutionary changes increased the cranial capacity of the human lineage from the small brain of Australopithecushuman ancestors of three million years agowhich was less than 500 cc in volume, to a brain nearly three times as large in modern humans. 2010;127:395403. Article Indices of DNA polymorphism (nucleotide diversity \(\pi\), mutation parameter \(\uptheta\), haplotype diversity \({\hat{\text{h}}}\) and number of haplotypes) were calculated with DnaSP v. 5.1 [23]. Diversifying selection refers to the situation in which natural selection favours different genotypes in different subenvironments. Beale H, Ostrander EA. Even 20 years after Wonderful Life was published I still see images of evolution that infer progress (especially the erroneous trajectory from chimpanzee to Australopithecus afarensis to Homo sapiens). 2011;2:450. The nearly universal success of artificial selection and the rapid response of natural populations to new environmental challenges are evidence that existing variation provides the necessary materials for directional selection. 2018;6:e4198. Google Scholar. Mol Ecol Notes. The lowest and highest levels of diversity among our data for Finnhorse were in trotters (HE=0.318) and pony-sized horses (HE=0.326), respectively. Genetic variability and history of a native Finnish horse breed. If readers of a popular book, for instance, were introduced to the branching diversity of a group and then shown the tracing of a particular lineage, that would not necessarily be bad. Breeders choose chickens that produce larger eggs, cows that yield more milk, and corn with higher protein content. 2005;93:314. The evolution of these resistant strains has taken place in the fewer than 400 years since the mines were first opened. Mitochondrial genomes from modern horses reveal the major haplogroups that underwent domestication. Based on nuclear SNP data, genetic differentiation among the four breeding sections was strongest between the draught horses and the three other sections (FST=0.0070.018), whereas based on mitochondrial DNA data, it was strongest between the trotters and the pony-sized and riding horses (ST=0.0540.068). Librado P, Fages A, Gaunitz C, Leonardi M, Wagner S, Khan N, et al. Directional selection is possible only if there is genetic variation with respect to the phenotypic traits under selection. In a recent study [47], also based on a 50-SNP window but using another SNP chip to detect homozygous segments of more than 500kb, the mean genome length covered by ROH was 305.1Mb and ranged from 227.5Mb in the Noriker breed (a heavy Austrian draught horse) to 396.5Mb in Purebred Arabians. Studies on many species have demonstrated that high levels of allelic variation are the exception rather than the rule in natural populations. This series presented undeniable evidence for the evolution of an animal familiar to all, but by what mechanism did the modern horse evolve? Although most of the imported horses were stallions because they had more breeding value, occasionally imported mares may have introduced their Central European or eastern mitochondria into the Finnish horse population. This result contradicted the findings of previous studies that have placed the Przewalskis horse as a sister taxon of domestic horses, with some possible gene flow from the domestic horse to the Przewalskis horse [39, 40]. Othman OE, Mahrous KF, Shafey HI. MN070243MN071106). Past and present effective population sizes were estimated with SNeP v.1.1 [32], by setting default values, for horses of each breeding section, horses that were not in the studbook, all the Finnhorses and all data (including the mixed breed group). the Founder Effect. The importance of horses led to a growing interest in their breeding and management. Science. Cookies policy. Part of A) . Haplotype network of the sequenced Finnhorses. For the other breeds for which we had more than 20 representatives, Shetland ponies were in haplogroups D, G, I, L, M, N and Q, warmblood trotters in A, B, G, I, L and N and Pura Raza Espaolas in B, G, L, N and Q (see Additional file 1). 3). This hypothesis was quickly scuttled by the collection of numerous fossil horses from the American west, particularly by paleontologist O.C. But you are right, orthogenesis can indeed be the "fruit in the tree" so to speak, the biologist's temptation to try to use an easier and more appealing explanation that the actual methodology. ScienceBlogs is a registered trademark of Science 2.0, a science media nonprofit operating under Section 501(c)(3) of the Internal Revenue Code. The number of Finnhorses declined strongly during the urbanization of Finland in the 1960s and 1970s, when people moved from rural areas into cities and agricultural and forestry practice began to use motorized horsepower instead of real horses. When Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 he faced a substantial problem. All the Finnhorses clustered together in the Bayesian clustering analysis and along the first principal component in the PCA analysis, and were separated from the other breeds that we studied here. However, the later formation of the four separate breeding sections likely increased genetic differentiation. Here are excerpts from their exchange. Directional selection is a type of natural selection in which the phenotype (the observable characteristics) of the species tends toward one extreme rather the mean phenotype or the opposite extreme phenotype. Average FIS, which was estimated with PLINK, ranged from 0.003 (pony-sized horses) to 0.027 (trotters). Simpson would later term the "tempo and mode" of evolution, yet such transitional creatures proved elusive. FIS-estimates from Arlequin were slightly different, ranging from 0.004 (trotters) to 0.014 (pony-sized horses) (see Table1). Druml T, Neuditschko M, Grilz-Seger G, Horna M, Ricard A, Mesari M, et al. mindemann Terms in this set (106) If the average leg size of a reptile continually got smaller through generations, this would be an example of directional selection. Compared to all other breeds, we found the smallest number of ROH in the Finnhorse breed, with an average number of 8.1 while it ranged from 11 to 38 in all the other breeds studied here (Table1) and (see Additional file 2), but in Finnhorses, the ROH were longer (on average 15,036kb), while they ranged from 6846 to 14,742kb in the other breeds. Helsinki: Otava; 1990 (in Finnish). In our study, the Finnhorses also cluster with the native Estonian horse and with the native British and Irish breeds (Fig. We are deeply in debt to all the horse owners, who provided us samples of their horses. If it is stopped altogether, natural selection gradually takes effect and turns the traits back toward their original intermediate value. 1999;41:958. A collared brown lemur (Eulemur collaris) baby, photographed at the Bronx Zoo. A better strategy is to have a population with one or a few genotypes that survive well in all the successive environments. Yet they maintain their genetic differentiation because nonresistant seedlings are unable to grow in the contaminated soil and, in nearby uncontaminated soil, the nonresistant seedlings outgrow the resistant ones. 2007;23:18016. Kvist, L., Niskanen, M., Mannermaa, K. et al. In the mitochondrial DNA dataset, the pairwise ST-values were significant between riding horses versus trotters and draught horses, and between pony-sized horses versus trotters and draught horses. The problem is to keep public scientific tomes simple, much of the family tree has to be pruned or mentioned only in passing, giving the erroneous idea of orthogenesis to the public. 2a, b). a) Codominance b) Dominant c) Incomplete dominance Tickln M. Get to know the Finnhorse. Accessed 10 Apr 2018. CAS The opportunity for directional selection also arises when organisms colonize new environments where the conditions are different from those of their original habitat. Google Scholar. The horse as an evolutionary paradox By laelaps on March 16, 2009. Laura Kvist. Update (09/14/10): After a few months of blogging on my own, I'm proud to say that Laelaps has made the jump over to the new WIRED, Important Update: The time has come to close things up here. In the domestic horse, it has been suggested that the large number of haplogroups and haplotypes spread over wide geographic regions results from a large number of mares having been incorporated into the domestic horse population [11, 12, 44]. Research in the Wolf lab focuses on the natural history and ecophysiology of desert animals. The climate became cooler and drier; the animal became an inhabitant of the plains. all of the genes and all of their associated alleles within a population represent the population's. Curr Biol. Suomenhevosen jalostus. Chang CC, Chow CC, Tellier LCAM, Vattikuti S, Purcell SM, Lee JJ. Thus, the history of the breed may have resulted in a high level of mitochondrial genetic diversity and in a large female effective population size. In practice, most Finnhorses are not evaluated before entering the studbook, but for an individual to be registered as a Finnhorse, it must trace back at least three generations of Finnhorses [15]. (Palaeotherium seemed like a good candidate for the evolutionary starting point for horses, but this was debatable.) Librado P, Gamba C, Gaunitz C, Der Sarkissian C, Pruvost M, Albrechtsen A, et al. 2004;4:1378. Species cope with environmental heterogeneity in diverse ways. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. As I said I think it was more of a framework used to understanding convergence and evolutionary "progress" and that is why it hung on so long. Csizmr N, Mihk S, Jvor A, Kusza S. Genetic analysis of the Hungarian draft horse population using partial mitochondrial DNA D-loop sequencing. It may indeed be possible to do this but it also requires some pruning and pushing extinct branches off to the sidelines. Across all samples, the average genotyping call rate was 0.988, after excluding three samples with call rates ranging from 0.355 to 0.419 (one mare and one stallion pony-sized Finnhorse and one mare Finnhorse that is not registered in the studbook; these individuals were not included in further analyses). Accessed 27 Apr 2018. Tenhunen S, Salonp T. Selection of Finnhorse stallions for cryopreservation. PLoS One. Horses were another matter. Article Suomen Hippos Ry, Gummerus, Jyvskyl; 2007. p. 35 (in Finnish). Diversifying selection often occurs in association with mimicry. 2a). Am J Hum Genet. The soil has become so contaminated that it is toxic to most plants, but the dense stands of bent grass growing over these refuse heaps have been shown to possess genes that make them resistant to high concentrations of lead and copper. Terms and Conditions, Which of the following is most likely to lead to two distinct species? Dr. Wolf:, "Nothing travels faster than light, with the possible exception of bad news, which follows its own rules." Pedigree-based inbreeding coefficients (\(F_{\text{ped}}\)) were obtained from the studbook provided by the Finnish trotting and breeding association [30] or calculated based on the pedigrees from a web portal of a pedigree database of horses that are registered mainly in Finland [31] with a minimum of six generations backwards. Among all the horses, we detected 249 haplotypes and 158 polymorphic sites, with a nucleotide diversity of 0.022 (SD=0.00016) and haplotype diversity of 0.982 (SD=0.0015). In: Saastamoinen M, editor. 2002;99:1090510. statement and Petersen JL, Mickelson JR, Cothran EG, Andersson LS, Axelsson J, Bailey E, et al. J Hered. Google Scholar. It actually behaved as if following out a program planned in advance. Heppa-jrjestelm. However, according to [6], the levels of heterozygosity and inbreeding in the Finnhorse breed are not markedly different from those of other horse breeds (HE=0.301, inbreeding coefficient FIS=0.004 and effective population size Ne=575 estimated from 27 Finnhorses, whereas the corresponding mean values for all studied breeds are equal to 0.295, 0.007 and 341, respectively). When the complete data was considered, the decline began slightly later, about 900 generations ago (Fig. Yang L, Kong X, Yang S, Dong X, Yang J, Gou X, et al. directional selection. Stabilizing selection is often noticeable after artificial selection. 2013;30:27259. Interestingly, haplogroup F, which so far was detected only in the Przewalskis horse, was present in four of the Finnhorses analysed here, of which three were not included in any of the breeding sections and one was registered as a riding horse. But females in many localities are conspicuously different from males; their wings lack tails and have colour patterns that vary from place to place. The smallest number of ROH in the other breeds (11) was found in a Royal Dutch Sport horse, spanning 92.0Mb. Accessed 9 Apr 2018. It is often used in agriculture and horticulture to produce a shift in the population mean of a trait desired by humans. The range and distribution of phenotypes then remains approximately the same from one generation to another. In this study, we examined the genomic and mitochondrial diversity of the Finnhorse, which is an all-round horse breed and the national horse breed of Finland. For blood samples, DNA was extracted with the Mobio BloodKit according to the instructions of the manufacturer (Mobio). Decline of genetic diversity in ancient domestic stallions in Europe. J Anim Breed Genet. From Yanoviak et al, 2008.In one of my favorite episodes of the animated TV show Futurama, the chief. This Extraordinary Claim Requires Extraordinary Evidence. No natural environment is homogeneous; rather, the environment of any plant or animal population is a mosaic consisting of more or less dissimilar subenvironments. By using this website, you agree to our gene flow from continent to . This attribute of populations is called genetic homeostasis. Gould opens with a discussion of images of progress in evolution and the strange relationship between scientists and illustration. The efficiency of diversifying natural selection is quite apparent in circumstances in which populations living a short distance apart have become genetically differentiated. All these haplogroups were considered as of European origin by [11] except for haplogroup Q, which has a more Asian or Middle Eastern distribution and is present, for example, in the Arabian horse. DNA was extracted from hair samples by cutting a ~1cm long piece from the follicle end of ~25 hairs from each individual, then putting them into 200L of QuickExtract solution (Epicentre) and following the protocol of the manufacturer. And then there's Dollo's Law, which states that you can't re-evolve a feature you've previously lost, which is why some birds evolve "false teeth" instead of just re-activating the dormant genes responsible for tooth expression. You can also shop using Amazon Smile and though you pay nothing more we get a tiny something. It is not explicit, but in this passage Cockerell proposes a compromise between orthogenesis and adpatation. PCR products were sequenced using the primer Eca_CR690_H, the BigDye Terminator v.3.1 kit and an ABI 3730 automatic sequencer (Applied Biosystems). The explanation for these differences stems from the fact that P. dardanus can be eaten safely by birds. Disruptive selection If a population recovers to its original population size after experiencing a bottleneck, which statement is correct regarding this population? PubMed fossils which show the horse has not changed in millions of years. Birds confuse the mimics with their models and do not prey on them. We are still grappling with paradoxical images that are supposed to reveal adaptation but more strongly imply some kind of predestined direction. The extremely low genetic variation of the horse Y-chromosome demonstrates that the domestic horse has only few paternal founders [7,8,9], whereas the genetic variation of the maternally-inherited mitochondrial DNA is very high [10,11,12]. This higher than expected level of heterozygosity and lower than expected inbreeding coefficient for a breed with strong directional selection and a recent decrease in population size have been explained by its within-breed genetic structure [6], i.e. A Blast search against GenBank for these Finnhorse sequences also resulted in best matches with the Przewalskis horse sequences (e: 0.0, identity: 626627/630bp). I will no longer be blogging for ScienceBlogs.com. Barbato M, Orozco-terWengel P, Tapio M, Bruford MW. Science. The existence of a Przewalskis horse haplogroup in the Finnhorse provides new insights into the domestication of the horse, and this finding supports previous suggestions of a close relationship between the Finnhorse and eastern primitive breeds. Although inbreeding in Finnhorses was lower than in many other horse breeds, the small nuclear effective population sizes of each of its breeding sections can be considered as a warning sign, which warrants changes in breeding practices. The three inbreeding coefficients estimated with PLINK and from pedigrees showed essentially the same pattern: Finnhorses were less inbred than the breeds in the mixed breed group (Finnhorses \(\hat{F}_{\text{I}}\)=0.050, SD=0.024, \(\hat{F}_{\text{II}}\)=0.032, SD=0.028, \(\hat{F}_{\text{III}}\)=0.009, SD=0.015 and \(F_{\text{ped}}\)=0.036, SD=0.015, mixed breeds \(\hat{F}_{\text{I}}\)=0.382, SD=0.025, \(\hat{F}_{\text{II}}\)=0.008, SD=0.025, \(\hat{F}_{\text{III}}\)=0.187, SD=0.025 and \(F_{\text{ped}}\)=0.057, SD=0.056). Suomenhevonen. Cieslak M, Reissmann M, Hofreiter M, Ludwig A. Colours of domestication. Directional selection occurs when one extreme phenotype is favored over another different extreme phenotype. A study of the genome-wide genetic diversity of 36 horse breeds [6] based on single nucleotide polymorphism (SNP) genotyping data showed that the diversity was low in breeds that have experienced high selective pressures, been closed populations, gone through a population bottleneck, or have low current census sizes (e.g., the Exmoor, Clydesdale and Florida Cracker breeds, with expected heterozygosity HE ranging from 0.236 to 0.291). A visual summary of horse evolution published in 1921 (derived from an earlier diagram by W.D. Limited number of patrilines in horse domestication. We thank also the Oulu Horse Hospital (Oulun Hevosklinikka Oy) for collaborating with sample collection and Minna Menp from the Finnish Trotting and Breeding Association for helping us to contact some of the horse owners. 2016;204:42334. Please make a tax-deductible donation if you value independent science communication, collaboration, participation, and open access. ), but readers come and go over time, and so I am jumping on board with the "Who, Blair Wolf is an associate professor of biology at the University of New Mexico. The mainly non-significant FST-values between the Finnhorse breeding sections suggest very weak, if any, differentiation among trotters, pony-sized horses and riding horses. Accessed 911 Aug 2017. 2018;13:e0201564. The red color of the gaster is not caused by a pigment, but thinning of the exoskeleton combined with the color of the nematode eggs. Population structuring was further studied with principal component analysis in PLINK 1.9, using the function pca and by calculating pairwise FST-values in Arlequin. The number of Finnhorses declined from over 400,000 in the 1950s to an all-time small number of 14,000 in 1987 [16], later increasing to the present number of approximately 20,000. Granted, when it was discovered, it was the first three-toed horse known, but as time went on and we found that there were numerous species of horses living alongside each other, several of them not exactly direct ancestors of the modern horse (compare Anchitherium and Parahippus, the latter is thought to have given rise to the modern equids and the former is thought to have kicked the bucket). its differentiation into four breeding sections. *[I have borrowed this phrase from paleontology. PLoS One. The mean sizes of ROH in kb (extending the set 1000kb size limit) are in Table1. This is a fine example of Directional selection . "It is unfortunate, and frustrating, that we appear to be stuck with images of evolution that imply progress." We performed the runs without LOCPRIOR, i.e. Selection intensity is a measure of the strength of directional selection applied in a selection experiment or breeding program to change a quantitative trait. His evolutionary mechanism predicted that the fossil record would contain finely-graded transitions revealing what G.G. Achilli A, Olivieri A, Soares P, Lancioni H, Hooshiar Kashani B, Perego UA, et al. Metzger J, Karwath M, Tonda R, Beltran S, gueda L, Gut M, et al. This is possibly due to a founder effect connected with the selection of horses that were included in the breed and in the breeding sections. There seems to be a continual fascination with how the present world came to be as it is; species or entire lineages that have been lost along the way are thus seem of little relevance. In many analysises I have seen, brontotheres are put as a sister group to horses and sometimes paleotheres, and chalicotheres are put as a sister group to the clade of rhinos+tapirs. 2b). We show that the female effective population sizes in the Finnhorse and its breeding sections are large, but that their nuclear effective population sizes are small and the genetic differentiation between the breeding sections remains low. Either horse evolution was truly being driven by natural selection or directional forces were mimicking true adaptation. This small effective size can result from only having four founding stallions for the breed but may also stem from recent breeding practices; although such practices were designed to avoid inbreeding, only five stallions have made approximately 50% of the genetic contribution during the 20052014 period (estimated from pedigree data based on the expected proportion of alleles in an individual originating from an ancestor [49]). When a new insecticide is first applied to control a pest, the results are encouraging because a small amount of the insecticide is sufficient to bring the pest organism under control. The modern horse has evolved from a small-bodied ancestor built for moving through woodlands and thickets to its long-legged descendent built for speed a the open grassland [Choose ) sexual selection artificial selection stabilizing selection directional; Question: Match the type of selection with the description. 2006-2020 Science 2.0. We found that the level of mitochondrial DNA variation was high in the Finnhorse, which confirms that the horse domestication in general involved a large number of mares, and the Finnhorse breed was founded using many local landraces. Der Sarkissian C, Ermini L, Schubert M, Yang MA, Librado P, Fumagalli M, et al. Many other butterfly species are noxious to birds, and so they are carefully avoided as food. All mitochondrial sequences are available in GenBank (Accession Nos. Contrary to a previous Bayesian skyline plot that was constructed from a mixture of breeds in [11] and showed a decrease in the female effective population size about 7000years ago and an increase thereafter, the female effective size in Finnhorses began to decrease approximately 300years ago. Biol Rev Camb Philos Soc. Proc Natl Acad Sci USA. Privacy statement. The process of directional selection takes place in spurts. All rights reserved. 2015;4:7. In addition, the decline in numbers until the 1980s created a population bottleneck, which possibly further decreased the genetic diversity and increased the effect of genetic drift. chapter 15 Bio: evolution on a small scale 5.0 (6 reviews) Which individual would be considered the fittest? "Worker Bee" by Motion City SoundtrackI have been writing here at ScienceBlogs.com for about two years and nine months now. Indeed, estimated heritabilities in the Finnhorse breed vary considerably from height at withers and at croup (0.89 and 0.90, respectively) to movement at walk and trot (0.13 and 0.18, respectively) [50]. Provided by the Springer Nature SharedIt content-sharing initiative. 2018;109:38492. Finnhorses are currently bred in four breeding sections: harness trotters (since 1965; 218 stallions and 1575 mares in 2017), riding horses (since 1971; 103 stallions and 611 mares), pony-sized horses (since 1971; 64 stallions and 219 mares) and draught horses (since 1971; 30 stallions and 103 mares [15]). In the PCA, some clustering of the trotters and pony-sized horses was observed, but when we estimated FST, FST-estimates were significant only for the comparisons between the draught horses and the others (Table4). These horses most likely had the same ancestry as the modern Friesian and Oldenburg breeds, including the Spanish ancestry that was used to create the Friesian breed [45]. Among the horses from the four Finnhorse breeding sections, the diversity parameters showed little variation, with nucleotide diversities being highest for draught horses and lowest for trotters and haplotype diversity and being lowest for pony-sized horses (Table2). Selection was subsequently directed towards traits that were specific to each breeding section (e.g., maximum withers height of 148cm for pony-sized horses, pulling capability for draught horses, athletic conformation for harness trotters and rhythmic, elastic and advancing gaits for riding horses [15, 17]). Eleven functional (limb) and four non-functional (facial) bilateral traits were measured on left and right sides in a cohort of 100 horses and ponies using callipers. Of all haplogroups (A to R, as defined in [11]), all haplogroups except O and K were present in the Finnhorses (Fig. Nevertheless, it is evident that the nuclear diversity of each of the Finnhorse breeding sections remains at a good level. The only non-significant comparisons were between the trotters, draught horses and non-studbook horses and between the riding and pony-sized horses. Purcell S, Chang C. PLINK 1.90 beta. Huxley was able to propose at least three evolutionary transitions among vertebrates supported by fossil evidence. Historically, King Gustav Vasa established stud farms in Finland as early as the 16th century, with horses being imported from the Netherlands and northern Germany, to increase the size of Finnish horses. To transform the obtained times into years and female effective size estimates into individuals, we used the minimum mutation rate of 2.9106 and maximum mutation rate of 10106 [26]. Ancient genomic changes associated with domestication of the horse. It is unfortunate, and frustrating, that we appear to be stuck with images of evolution that imply progress. Mol Biol Evol. Within each Finnhorse breeding section, the values of expected heterozygosity from the SNP data were lowest for the trotters (0.318) and highest for the pony-sized horses (0.326). http://www.hippos.fi/in_english. 2010;10:5647. Resistance to one or more pesticides has since been recorded in several hundred species of insects and mites. Gaunitz C, Fages A, Hanghj K, Albrechtsen A, Khan N, Schubert M, et al. Domestication has influenced the behaviour, morphology, physiology and performance of a species through selective breeding. In the following millennia horses spread across the ancient world, and their role in transportation and warfare affected every ancient culture. Marsh. Mol Ecol. Accessed 20 May 2018. The discovery of the skeleton of the dinosaur-like bird Archaeopteryx in 1861 alone showed that the fossil record held many secrets left to be revealed. Your US state privacy rights, J Genet Eng Biotechnol. 2009;25:14512. directional selection. The small dinosaur Compsognathus, for instance, was not a bird ancestor but a dinosaur representative of the kind of animal from which birds evolved. (See my review of The People's Peking Man for some brief thoughts on fossils and national pride.). I think this relates to the Victorian view of history as a march of progress. Article Lippold S, Matzke NJ, Reissmann M, Hofreiter M. Whole mitochondrial genome sequencing of domestic horses reveals incorporation of extensive wild horse diversity during domestication. 2019;220:5766. 2004;36:3356. 2005;14:261120. 1) and (see Additional file 1). that's no reason to show it first in the list). Contributions are fully tax-deductible. Proc Natl Acad Sci USA. Nat Commun. 2011;86:88599. Finally, 37,445 SNPs remained for further analyses, unless stated otherwise. For example, the breeder might select . From An Introduction. We are grateful for the priceless help from Laura Trml, Soile Alatalo and Hannele Parkkinen-Oinas in the lab. I can comfortably criticize orthogenesis now, but it was a compelling idea once upon a time. Pritchard JK, Stephens M, Donelly P. Inference of population structure using multilocus genotype data. When individuals with intermediate phenotypes are favoured and extreme phenotypes are selected against, the selection is said to be stabilizing. Analysis of the mitochondrial sequences resulted in the alignment of a 631-bp long fragment from 743 Finnhorses and 121 horses of other breeds (fowls excluded). the gradual increase in size over millions of years.

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