(Visited 969 times, 1 visits today)FacebookTwitterPinterestSave分享0 A new study of elephants, mammoths and mastodons show they were all interfertile or capable of hybridization.Our present world is impoverished of elephants, or “elephantids” as scientists dub the family. Mammoths and mastodons roamed throughout America and Asia, evidenced by the massive fossil beds, where millions of mammoth bones can be found in permafrost. Some in the frozen tundra from Alaska to Siberia still retain soft tissue, organs and hair. These days, the two remaining species of elephants are primarily restricted to Africa and India.Art of mammoth and mastodon types found at La Brea Tar Pits, California. Photo by David Coppedge.How different are the extant types of elephants from the extinct types, such as mammoths and mastodons? With genomics, scientists can begin to answer the question. “A comprehensive genomic history of extinct and living elephants” with no less than 37 co-authors has been published in the Proceedings of the National Academy of Sciences (PNAS). The findings show a surprising amount of gene flow (i.e., sex) has taken place between the different branches on the elephant tree.Elephantids were once among the most widespread megafaunal families. However, only three species of this family exist today. To reconstruct their evolutionary history, we generated 14 genomes from living and extinct elephantids and from the American mastodon. While previous studies examined only simple bifurcating relationships, we found that gene flow between elephantid species was common in the past. Straight-tusked elephants descend from a mixture of three ancestral populations related to the ancestor of African elephants, woolly mammoths, and present-day forest elephants. We detected interbreeding between North American woolly and Columbian mammoths but found no evidence of recent gene flow between forest and savanna elephants, demonstrating that both gene flow and isolation have been central in the evolution of elephantids.This is the first comprehensive genomic assessment of the relationships between elephants, the iconic symbol of megafauna (large animals). Evolutionists have assumed a Darwinian branching tree, with species diverging and going off on their own. What the genomes show, however, is that “interspecies hybridization has been a recurrent feature of elephantid evolution.” That’s not the kind of evolution Darwin promoted. Some cases were contrary to what evolutionists used to believe:Model of Columbian mammoth displayed at Hot Springs Mammoth Site, South Dakota. Photo by David Coppedge.We found that the genetic makeup of the straight-tusked elephant, previously placed as a sister group to African forest elephants based on lower coverage data, in fact comprises three major components. Most of the straight-tusked elephant’s ancestry derives from a lineage related to the ancestor of African elephants while its remaining ancestry consists of a large contribution from a lineage related to forest elephants and another related to mammoths. Columbian and woolly mammoths also showed evidence of interbreeding, likely following a latitudinal cline across North America.What they have found is more of a network of genetic relationships rather than a branching tree. Isolation, however, can lead to genetic distance, to the point where hybridization or infertility results.While hybridization events have shaped elephantid history in profound ways, isolation also appears to have played an important role. Our data reveal nearly complete isolation between the ancestors of the African forest and savanna elephants for ∼500,000 y, providing compelling justification for the conservation of forest and savanna elephants as separate species.Hybridization is causing reassessment of what constitutes speciation. Evolution News & Science Today reported on a remarkable case of finches from New Guinea, where several indigenous species that look more different from each other than the famous Galapagos finch species are still capable of interbreeding or hybridization. A more general article on Evolution News discusses how hybridization is “weaving Darwin’s tree into a web” and making Ernst Mayr turn over in his grave. In his mission to advance Darwinism, the eminent evolutionist saw hybridization as a dead end, because he expected to see Darwin’s tree leading to reproductive isolation. Now, however, biologists are finding that some hybrids are able to produce fertile offspring. These, in turn, can “introgress” back into the ancestral species. Science Magazine says we may be on the cusp of a “third wave of a scientific revolution in biology.” New findings about hybridization, as in the case of elephantids reported above, are “shaking up the tree of life” and “challenging evolutionary theory.”Traditionally, individuals that can interbreed are considered one species. What, then, should be said of all the diverse elephant species, if gene flow occurred between them? When you think of the morphological differences between dogs, which are all one species (Canis familiaris) artificially selected for traits desirable to humans, it becomes evident that potential for variability in a single parent species can be enormous. And yet we never see a dog becoming a non-dog, or an elephant becoming a non-elephantid.A similar situation is coming to light in our own species, Homo sapiens. Where evolutionists have long split species of Homo into Neanderthals, erectus, Denisovans and a few others, new genomic studies are showing them all to be one interfertile type. Just a few days ago, for instance, it was reported that “Modern humans interbred with Denisovans twice in history” (Science Daily). Welcome to the family! As Live Science puts it, “Neanderthals Weren’t Humans’ Only Mating Partners. Meet the Denisovans.”Modern genomics is revealing networks of interfertile varieties within types that can become isolated, change, and then back-cross into their same type. It’s a very different picture from the tree metaphor of Darwin, who envisioned species branching off and going their separate ways, becoming reproductively isolated.Sign about “island dwarfism” in mammoths at Hot Springs Mammoth Site, South Dakota. Dates are disputable. Photo by David Coppedge.The picture fits the creation science called baraminology, which seeks to identify the basic types of organisms that correspond to what Genesis calls “kinds” that reproduce true to their kind. Modern creationists do not subscribe to the idea of “fixity of species” which is clearly unsupportable. Even ardent Biblical creationist Ken Ham thinks that the animals that went onto Noah’s Ark would have looked very different from living representatives of their kind. Dr Randy Guliuzza of ICR proposes that the Creator programmed variability into each type so that it could thrive as it spread into new environments. That’s programming, not “natural selection” (the “Stuff Happens” Law). Creationists also believe that substantial changes can occur rapidly. Look how quickly all the human varieties (not “races”) became accentuated since the Tower of Babel, and yet all humans remain interfertile. In extreme cases, we know that Europeans easily married native Americans in both North and South America, and had healthy children, even though they came from families that had migrated in opposite directions around the globe thousands of years ago. As creationists have loosened up on their ideas of allowable variability within kinds, evolutionists are facing contradictions to their long-held views about speciation. Genomic evidence is tangling up their beloved tree of life, weaving it into a bush with interconnected branches. Genetic evidence (including epigenetic processes the early evolutionists knew nothing about) appears consistent with rapid variation within created kinds, with programmed variability that allows for adjusting to new environments. That’s design, not evolution as Darwin viewed it. There’s no upward progress from bacteria to man (or elephant), just variations on themes set during the Creation week of Genesis.