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Why similarities among organisms led scientists to believe that organisms are evolved?

Why similarities among organisms led scientists to believe that organisms are evolved?


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Theory of evolution states that organisms are evolved into other more advanced ones over time because there are some traits in modern organisms resemble with organisms existing before (from fossil record). But it might be possible that each organism has created independently of each other. why similarities mean evolutionary relationship?


I will answer by explaining some misconceptions in your original question:

Theory of evolution states that organisms are evolved into other more advanced ones over time

Nope that's not what the theory of evolution is stating, mainly because the expression "more advanced" does not mean much and also is a loaded expression. You might want to start with an intro course to evolutionary biology to understand what the theory of evolution says. Understanding Evolution is a very introductory course you might like

@Remi.b Alright I will have a look at what theory of evolution states but the basic thing is humans are thought to have evolved from chimpanzees. What I want to know is chimpanzees might resemble to humans but why chimpanzees are considered ancestor of humans? It might be possible that humans and chimpanzees created individually?

No, the theory of evolution does not state that humans evolved from chimpanzees. It says that humans and chimpanzees / bonobos have a common ancestor (about 6 millions years ago) that was not a human, nor was it a chimpanzee or a bonobo.

You can find an introduction to phylogenetics in this post and you can find online tools to visualize the tree of life in this post.

Philosophical issue in your question

The theory of evolution makes predictions that have been tested and demonstrated correct. You are asking why would creationism would not lead to the same predictions. For this purpose, one need to know what predictions would creationism make but this is very much undefined. If you can point to specific predictions that creationism would make, then we could tell you whether we have a counter evidence. The issue is that there is always a way to say, everything has been designed so that it looks like evolution is at play even if species were created anew. But this is not falsifiable.

So, maybe you might want to make specific predictions, that in your opinion, would be congruent with creationism but not with the theory of evolution and then we can tell you if we have evidence to support this prediction.

Related posts

While it does not directly answer your question (because IMO, for semantic issue, the question is unanswerable), you might want to have a look at Is evolution a fact? and Demonstrable and repeatable examples of evolution


The main reason organisms not believed to be created independently, (besides no evidence for a creator to do creating) is that organisms do not just share similarities but they share similarities in a predictable pattern. Similarities are not random but follow a pattern that only makes sense if it is due to small changes over long periods of time in an ancestors/descendants branching tree of relationships. Two similar creatures will be equally similar to a third, and those three will be equally similar to a fourth and so on ans so forth in a nested pattern, not just a random assortment.

Humans might happen to be very similar to chimpanzees and vice versa by chance alone, but the chance of both humans and chimps also being very similar to gorilla is much less likely, them being similar in the same ways is even less likely, and the chance of all three also each being very similar to orangutan is even less likely, ect and so forth through the entirety of life. The chances of this arrangement of traits and genes happening by chance (aka without any actual relatedness or common origin) is so astronomically small it is difficult for us to even conceive of events that uniquely unlikely. There is a better chance of all your atoms happening to sync up so you fall/phase through your chair and plummet to the center of the earth in the next few minutes. In fact the entire field of Cladistics is about testing and mapping these relationships, and one of the things they constantly test against is a the possibility of an random or convergent assortment of trait.

This pattern also mirrors the pattern of human driven evolution (artificial selection) in which organisms are bred from other ancestral organisms through small changes by encouraging individuals with certain traits to reproduce and discouraging others, which at the time was far more well understood, which is how they recognized it. It is also why three chapters of Darwin's book was about show pigeon breeding.

And all that is before you get into things like the mathematical predictability of evolution, the fossil record, or directly observed evolution.


Biology: Comparative Morphology: Studies of Structure and Function

Morphology, one of the life sciences, studies an organism's outward characteristics: its anatomy, shape, and appearance. One of the first steps in identifying an organism is examining these prominent features this helps distinguish one species from one another and identify new species or subspecies. Morphology can also be studied on a much smaller scale, investigating specific organs, tissues, or cell types.

The ability to compare the morphology of two organisms is an important basic skill for life scientists. Simple, careful observation and comparison have led, for example, to most of the discoveries in the field of paleontology as well as the discovery that whales are mammals.


Examples of Organisms

The more closely organisms are related, the more similar the homologous structures are. Many mammals, for example, have similar limb structures. The flipper of a whale, the wing of a bat, and the leg of a cat are all very similar to the human arm, with a large upper "arm" bone (the humerus in humans) and a lower part made of two bones, a larger bone on one side (the radius in humans) and a smaller bone on the other side (the ulna). These species also have a collection of smaller bones in the "wrist" area (called carpal bones in humans) that lead into the "fingers" or phalanges.

Even though the bone structure may be very similar, function varies widely. Homologous limbs can be used for flying, swimming, walking, or everything humans do with their arms. These functions evolved through natural selection over millions of years.


How and why single cell organisms evolved into multicellular life

Throughout the history of life on Earth, multicellular life evolved from single cells numerous times, but explaining how this happened is one of the major evolutionary puzzles of our time. However, scientists have now completed a study of the complete DNA of one of the most important model organisms, Gonium pectorale, a simple green algae that comprises only 16 cells.

This microscopic organism is helping to fill the evolutionary gap in our understanding. The two year research project was a global collaboration between Kansas State University, Universities of Arizona and Tokyo, and Wits University. It is documented in the journal Nature Communications.

Pierre Durand, a researcher in the department of Molecular Medicine and Haematology and the Evolutionary Studies Institute at Wits University is one of the project collaborators.

"The evolution from unicellular to multicellular life was a big deal. It changed the way the planet would be forever. From worms to insects, the dinosaurs, grasses, flowering plants, hadedas and humans, you just have to look around and see the extraordinary forms of multicellular existence," says Durand.

"It has been difficult to explain how this occurred because it was not an easy thing to have happened. So questions like 'why did single cells live together in groups at the very beginning of multicellularity when it puts them at a fitness disadvantage?' challenged us for a long time," says Durand. We still don't know most of the answers but this project has certainly filled one of the gaps in our current understanding.

There are many model systems for studying multicellularity but nothing quite like the volvocine green algae, the group to which G. pectorale belongs.

"The evolutionary transition to multicellularity has occurred numerous times in all domains of life, yet the evolutionary history of this transition is not well understood. However, the volvocine green algae include a diverse variety of unicellular, colonial, and multicellular species," says Durand.

There are many members of the volvocines with varying degrees of complexity, so it is possible to examine different stages on the road to multicellularity. The volvocines also evolved relatively recently (during the Triassic period about the time when the first dinosaurs appeared) and the mysteries of multicellularity are not lost in evolutionary time.

Reporting on the genome sequencing of Gonium pectorale, the scientists uncovered some of the genes that regulate cellular growth and division in this organism. This finding helps explain how single cells live together in groups -- one of the earliest steps on the path to a multicellular existence.


Advantage to Colony

Even though the individual single-celled organisms remained separate and could survive independently, there was some sort of advantage to living close to other prokaryotes. Whether this was a function of protection or a way to get more energy, colonialism has to be beneficial in some manner for all of the prokaryotes involved in the colony.

Once these single-celled living things were within close enough proximity to one another, they took their symbiotic relationship one step further. The larger unicellular organism engulfed other, smaller, single-celled organisms. At that point, they were no longer independent colonial organisms but instead were one large cell.

When the larger cell that had engulfed the smaller cells started to divide, copies of the smaller prokaryotes inside were made and passed down to the daughter cells.

Eventually, the smaller prokaryotes that had been engulfed adapted and evolved into some of the organelles we know of today in eukaryotic cells such as the mitochondria and chloroplasts.


Similarities Among Living Organisms

The sea gull and the pelican are very similar in appearance, behavior and DNA. The differences, such as beak shape and size, show that each bird adapted to fit its own environment.

One type of evidence for evolution (evidence that organisms are related, descended from a few common ancestors, and change to adapt to their environments) is that organisms are similar to each other, but not exactly the same. Similar organisms have differences that help them adapt to their environments.

Many organisms have similar body plans. Horses', donkeys', and zebras' bodies are set up in pretty much the same way, because they are descended from a common ancestor. As organisms adapt and evolve, not everything about them changes. The differences, such as the zebra's stripes, show that each species adapted to its own environment after branching off from the common ancestor.

The bodies of deer, moose, zebras, and horses are very similar, and these animals are very closely related. One major difference is that deer and moose have antlers and zebras and horses don't. Why is this? Deer and moose live alone or in small groups, while zebras and horses live in large herds. Living in a herd provides its own protection from enemies: it is easier to attack an individual than a huge herd. Therefore, herd-living animals do not need the antlers that their loner relatives need for protection. In addition, running or grazing with large antlers is hard to do in a herd, where it is easy to accidentally stab one's neighbor.

All insects have heads, abdomens, and thoraxes, antennae, six legs, and wings. However, each species is different, and while all insects have wings, some have small, useless wings, because their environments did not force them to evolve useful wings, or because their wings became harmful to survival.

All birds have feathers, beaks, and wings, but are different because they had to adapt to different environments, such as the webbed feet of water birds but not of land birds. On a more distant level, fish and zebras both have eyes, frogs and baboons both have spines. Generally, the longer ago the last common ancestor lived, the less the organisms have in common. Turtles and tortoises share a common ancestor, but began evolving separately a long time ago. The common ancestor of box and painted turtles lived more recently, so the box turtle has more in common with the painted turtle than it does with the tortoise. How similar two organisms are can help people figure out how closely they are related.


Repeatable Evolution or Repeated Creation?

Any casual observer of nature recognizes that many creatures bear some resemblance to one another. Many species of frogs, lizards, fish, and other animals and plants from different parts of the world appear to be nearly identical. This similarity has been the pattern throughout life’s history. Recent biological studies have shed light on the nature of this physical resemblance and carry significant apologetic implications. Many species that look identical are, in fact, genetically different, and therefore unrelated. In accounting for these unexpected differences, evolutionary biologists have proffered inadequate explanations. This article will discuss a few of the many recent discoveries that continue to buttress the case for a biblical Creator while continuing to erode the foundation for the evolutionary paradigm.

According to evolutionary theory, organisms that possess identical morphologies (forms or structures) must share a common ancestry. Evolutionary biologists, therefore, have employed morphological systematics––the study of the relationships among organisms according to physical characteristics––when classifying species, and thus have concluded that similar groups share common ancestry. However, with the advent and widespread application of molecular systematics, in which DNA sequences are used instead of morphologies to determine biological relationships, science now is beginning to identify an increasing number of challenges to the evolutionary classification. Biologists are uncovering numerous examples of organisms that cluster together morphologically (structurally), and yet are genetically distinct. Frogs, lizards, or herbs that appear to be identical are actually different at the genetic level. An evolutionary interpretation of this data, then, demands that the morphologically identical organisms must have evolved independently of one another in a “repeatable” fashion.

The Contingent Nature of the Evolutionary Process

The evolutionary paradigm cannot accommodate “repeatable” evolution. When evolutionists observe a tree frog ideally suited for its environment, they assert that natural selection––environmental, predatory, and competitive pressures repeatedly operating on random inheritable variations for long periods of time––has led to this relationship. Chance governs the evolutionary process at its most fundamental level. Because of this, it is expected that repeated evolutionary events will result in dramatically different outcomes. The concept of Historical Contingency embodies this idea and is the theme of Stephen J. Gould’s Wonderful Life:

“…No finale can be specified at the start, none would ever occur a second time in the same way, because any pathway proceeds through thousands of improbable stages. Alter any early event, ever so slightly, and without apparent importance at the time, and evolution cascades into a radically different channel.” 1

Gould’s metaphor of “replaying life’s tape” asserts that if one were to push the rewind button, erase life’s history, and let the tape run again, the results would be completely different. 2 The very essence of the evolutionary process renders evolutionary outcomes as nonreproducible (or nonrepeatable). Therefore, “repeatable” evolution is inconsistent with the mechanism available to bring about biological change.

A Test for Evolution, A Test for Creation

The idea of Historical Contingency suggests that one powerful way to discriminate between the “appearance of design” that results from the evolutionary process and Intelligent Design is to determine if contingency is operating in the biological realm. 3 If life is exclusively the result of evolutionary processes, then biologists should expect to see few, if any, cases in which evolution has “repeated” itself. This is simply not the case. During the last six years numerous examples of “repeatable” evolution have come to light as molecular data has been increasingly used in biological systematics. These findings demonstrate that the evolutionary paradigm fails the test of contingency. The discovery of morphologically identical, yet genetically unrelated organisms does, however, offer powerful support for biblical creation. These examples of “repeatable” evolution include anolis lizards, ranid frogs, cichlids, sticklebacks, mangabeys, river dolphins, and Pericallis, an island plant.

Anolis Lizards

Anolis lizard species found on the islands of the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto Rico) are perfectly adapted to fit into six distinctive ecological niches. 4 A species that is perfectly suited for a particular ecological niche is termed an ecomorph. Two examples of Anolis lizard ecomorphs found on the Greater Antilles are small lizards with short legs that live on fragile twigs, and large lizards with large toe pads that occupy the crowns of trees. Morphological analysis of the Anolis lizards that populate the Greater Antilles reveals objectively recognizable groups of ecomorphs. 5 Based on their morphological features (or close resemblance), members of the same ecomorph grouping from the different islands were found to be more closely related to one another than lizards from the same island.

Given the contingent nature of the evolutionary process, therefore, it would be expected that each ecomorph evolved a single time from an ancestral species. Each ecomorph produced by a single evolutionary sequence of events would have then dispersed among the islands of the Greater Antilles. However, when this model was tested by comparing mitochondrial DNA sequences of the different Anolis species, it was discovered that lizards in the same ecomorph class were not related to one another. 6 This study concluded that it would have taken at least 17-19 separate evolutionary pathways to produce all the Anolis ecomorphs, if natural process evolution was the explanatory agent. Commenting on this work, biologists P.H. Harvey and L. Partridge, state, “It seems that as the tape of life has been replayed in separate islands, there has been a remarkable amount of convergent evolution.” 7

Ranid Frogs

Ranidfrogs––comprised of over 1000 species––are common throughout the world. These frogs have adapted to a wide range of lifestyles and habitats. Two of the Ranid subfamilies, Rhacophorinae (tree frogs) and Tomopterninal (burrowing frogs) are found both in Madagascar and on the Indian sub-continent of Asia. They are nearly indistinguishable in their morphological, physiological and developmental characteristics and form two groups of ecomorphs.

Frogs, specifically, and amphibians, in general, cannot migrate through salty environments. Therefore, it has long been held, from an evolutionary standpoint, that the tree frogs and burrowing frogs evolved prior to the separation of the Madagascar-Seychelles-Indian tectonic plate from Gondwanaland (the earth’s one land mass prior to tectonic separation). It is believed that this tectonic plate drifted away from Gondwanaland about 130 million years ago, separated to form Madagascar, and finally attached onto Eurasia to form the Indian sub-continent. Some tree and burrowing frogs were passively carried along and became isolated from one another.

Nuclear and mitochondrial DNA analyses of Madagascar and Indian Ranid frogs demonstrate, however, that the evolutionary explanation is untenable. 8 DNA sequence analysis clusters these ecomorphs based on geography not morphological features. In other words, from an evolutionary perspective, burrowing frogs and tree frogs in Madagascar and India must have evolved independently. This same study has also identified examples of “repeated” evolution for Ranid ecomorphs located in Sri Lanka and India. 9 Even more amazing, researchers conclude from the DNA sequence analysis that the larval characteristics of several Madagascar and Indian ecomorphs are also identical. This means that the complex developmental pathways and larval lifestyles must have evolved independently on several occasions to produce the same result––if the data is viewed from an evolutionary perspective. 10

Cichlids

Cichlids––freshwater fish that are widely diverse in form, color and habits––are scattered throughout the Southern Hemisphere. 11 Numerous examples of cichlid ecomorphs have been recognized in lakes Victoria, Malawi and Tanganyika of East Africa. An evolutionary explanation would postulate that each of the ecomorphs evolved a single time and then was independently isolated in each lake after water levels subsided, causing a single lake to split into three geographically separated lakes. 12

Sequence analysis of mitochondrial DNA, however, indicates that the ecomorphs found in the three East African lakes must have evolved independently, multiple times, assuming an evolutionary explanation. 13-15, 16-17 Also, researchers have noted the independent emergence of ecomorphs for cichlids in two lakes in Cameroon. 18 Even more striking is the recent recognition that multiple independent origins occurred for ecomorphs within different regions of a single lake, Tanganyika. 19 That is, from an evolutionary perspective, some cichlid species in Lake Tanganyika are viewed as separate, morphologically indistinguishable species that “evolved” in exactly the same way multiple times.

Like the cichlids, scientists believe the sticklebacks species found in British Columbia evolved several times independently to produce the same ecomorphs. The same two stickleback species, bulky benthic (bottom-dwelling) feeders and streamline open-water feeders, live in isolated lakes near the Pacific coast of British Columbia. The standard evolutionary explanation maintains that these two species evolved from one marine stickleback species, became trapped and isolated in the lakes after sea levels changed, and then independently populated the lakes. 20 Mitochondrial DNA analysis provides results contrary to the most plausible evolutionary explanations. 21 These results indicate that the stickleback species from the same lake have a greater degree of genetic similarity than do morphologically identical species from different lakes. From an evolutionary viewpoint, therefore, stickleback ecomorphs in the isolated lakes must be the product of “reproducible” evolutionary events.

A recent breeding experiment affirms the previous conclusion. 22 In a laboratory environment, researchers discovered that corresponding ecomorphs from different lakes attempt to interbreed with one another, while eschewing the different ecomorphs that share their lakes. This result is interesting in light of the biological definition of a species. Biologically, a species is considered to be an interbreeding population of individuals. The willingness of the same ecomorphs from different lakes to interbreed points to just how profound the similarity is among the stickleback ecomorphs––both morphologically and behaviorally.

Mangabeys

Mangabeys are large Old World monkeys found in Africa. Morphological similarity has traditionally led biologists to place all the mangabey species into a single genus, Cercocebus. Baboons, drills, mandrills, and geladas are closely related to mangabeys. Earlier molecular studies and mitochondrial DNA sequence analysis challenged the morphologically based classification that places mangabeys into a single group. 23- 24 These studies indicated that the single mangabey genus should have been separated into two groups, and that the nearly identical mangabey morphologies must have evolved independently two times. Recent nuclear DNA analyses have confirmed that mangabey morphology “evolved” on two separate occasions, when viewed from the evolutionary paradigm. 25

These results not only support two morphologically indistinguishable genera, Cercocebus and Lophocebus, but also indicate that the strong morphological similarities of drills, mandrills and baboons must have evolved independently as well. Nuclear DNA sequence analysis aligns drills and mandrills with the mangabey genus, Cercocebus, and baboons and geladas with the mangabey genus, Lophocebus. 26 Inspired by the results of the molecular studies, two biologists have recently recognized subtle morphological differences in dental features and in the arm and leg bones of the Cercocebus and Lophocebus mangabeys. 27 However, these skeletal and dental differences are so slight that without the supporting DNA sequence data it is questionable if these differences would have been recognized at all, let alone accepted as significant.

River Dolphins

Unlike other marine mammals (whales, porpoises, and dolphins), river dolphins live in freshwater, river environments. There are four extant river dolphin species. Three of these species live exclusively in freshwater and one (the La Plata dolphin) lives both in estuaries and coastal waters. The freshwater dolphins inhabit the Ganges and Brahmaptura Rivers of India, the Yangtze River of China, and the Amazon River.

River dolphins share similar and characteristic morphologies. The most commonplace view among biologists is that the river dolphins emerged from a single evolutionary pathway. Mitochondrial and nuclear DNA sequence analysis now demonstrates otherwise. 28 In other words, if the DNA sequence data is interpreted within an evolutionary context, the four river dolphin species must have evolved the same characteristic features independently and repeatedly.

Pericallis

Pericallis, a genus of plants related to sunflowers, are found in the Macaronesian archipelago (Azores, Canary Islands, Cape Verde, Madeira and Selvagens) off the west coast of Africa. 29 Of the Pericallis species found in the Macaronesian islands, six are woody and nine are herbaceous. This is not surprising, since many island plants are woody variants of mainland herbs or soft-bodied plants.

The most reasonable evolutionary explanation for the origin of Pericallis woodiness is that it evolved on the mainland and found its way to the Macaronesian islands. However, nuclear DNA sequence analysis betrays this explanation by revealing no genetic similarity. When examined employing evolutionary assumptions, therefore, the data indicates that Pericallis woodiness musthave evolved on at least two separate occasions. 30

Evolutionary Attempts to Account for Repeatable Evolution

In isolation, each case of “repeatable” evolution can be viewed as an oddity and poses no real threat to the “truth” of biological evolution. However, the many cases of “repeatable” evolution––in which entire organisms seem to evolve independently and reproducibly––simply doesn’t follow, given the nature of the mechanism available to drive the evolutionary process, chance. Biologists who embrace methodological naturalism––the notion that only natural explanations can be used to account for phenomena in the physical and material world––do indeed regard the occurrences of “repeatable” evolution as unexpected and remarkable. However, their philosophical predisposition does not allow them to be open to the possibility that a Creator is responsible for the repeated occurrences of ecomorphs found in nature. These morphologically indistinguishable, yet genetically distinct ecomorphs can be properly considered as one of the many fingerprints that the Creator has left on His creation. In fact, if a single Creator was responsible for life, one could anticipate seeing repeated examples of the same blueprint throughout the biological realm. One would expect that a single Creator would reuse successful designs over and over again.

Given the examples cited previously, evolutionary biologists cannot seem to account for “repeatable” evolution. One attempt at explaining this phenomenon is to attribute “special” capability to the forces of natural selection. 31 Since organisms are perfectly suited for their ecological milieu, and therefore more likely to survive to reproductive age, it is thought that the forces of natural selection––competitive, predatory, and environmental influences––repeatedly “channel” the evolutionary process down the same pathway to produce the same organisms. This explanation for recurrent evolution neglects the fact that selective forces are nothing more than a blind filter. Natural selection can only operate on traits made available by random changes in the population’s genetic makeup. It is not likely that these changes would be repeatable, given the complexity of genomes, nor that they would occur in the same historical sequence.

Additionally, it is unlikely that the factors that made up an organism’s ecology would be identical throughout time. Changes to the ecological environment in Madagascar, for example, would not be identical to the changes in the ecological environment in India. The components of natural selection are influenced by chance and by history. Therefore, natural selection would not be expected to guide separate evolutionary sequences and then produce morphological traits in an organism that somehow remarkably converge.

One well-known experiment with bacteria has led evolutionary biologists to conclude that natural selection can direct the convergence of features in the evolutionary process. 33 These experiments demonstrated that bacterial populations subjected to identical environments achieved similar fitness (a measure of the ability of an organism to survive) regardless of chance, mutational events, and history. However, the conclusion drawn from these experiments does not support such a directive role for natural selection for two reasons.

First, fitness is different from morphological characteristics. Fitness describes the capability to survive independent of the organism’s features. It is not surprising that natural selection converges on optimal fitness in mathematical modeling or when characterizing the response of bacteria to environmental stress. Yet, it does not follow that convergence to optimal fitness explains the improbable convergence of morphological features. Second, what is true for bacterial communities (single cell organisms that are morphologically nondescript, comprised of large population sizes, and short generation times) is not necessarily true for the advanced multi-cellular organisms that have been shown to display “repeatable” evolution. 33 The population and reproductive characteristics of these advanced, complex organisms preclude their capability to evolve.

Another attempt to account for “repeatable” evolution within the evolutionary paradigm is based on inherent biological and developmental constraints. 34 The idea is that these constraints only allow certain variations to occur in the evolutionary process. When evolution occurs, then, it can only produce a limited number of ecomorphs, therefore the same ecomorphs result repeatedly. This explanation falls short. Developmental and inherent biological constraints would have no “knowledge” of the environmental, predatory, or competitive pressures facing the organism. Therefore, one would not expect there to be ecomorphs. In the face of this explanation one must ask, “Why do we see organisms that are perfectly suited to their ecological niche?” The universal occurrence of perfect adaptation is inconsistent with any limitations on biological variation.

Conclusion

Prior to the influence of Charles Darwin (Origin of Species was first published in 1859) scientists viewed the nature of the similarities among organisms as due to the variation of a fundamental design or archetype. 35 This “blueprint” for life was acknowledged as having come directly from the mind of God. Organisms classified within a particular grouping were viewed as variations of the design provided by the Creator.

When the tide began to shift toward Darwinian evolution, however, biologists came to understand the relationships among organisms as reflecting descent with modification from a common ancestor. The ancestral species that gave rise to a group of related organisms replaced the archetype, and natural selection operating on random biological variation replaced the creative hand of God.

As both evolutionists and creationists seek to account for the features found in the biological realms, different predictions flow consequentially from these explanations. Chance and a historical sequence of events control biological evolution, at its essence. One would expect therefore, few, if any, instances in which the evolutionary process would repeat itself. On the other hand, if a single Creator were responsible for life on earth, one would expect to see recurrent design throughout nature.

The widespread availability of molecular systematics now allows scientists to test these two interpretations of nature. As molecular systematics is used increasingly to characterize the relationship among organisms––both living and extinct––numerous examples of morphologically identical and genetically distinct groups are being uncovered. The widespread occurrence of repeatable evolution cannot be accommodated within the evolutionary paradigm. Any attempt to account for this phenomenon from a naturalistic standpoint violates the very nature of the evolutionary process or has implications that are inconsistent with what biologists observe in nature.

The evolutionary paradigm fails in the face of the discovery of “repeatable” evolution while biblical creation gains support from this phenomenon. What is interpreted as “repeatable” evolution––morphologically indistinct and genetically unique organisms––is what one would expect if a single Creator has generated life throughout Earth’s history. As time goes on, scientists expect to see more examples of “repeatable” evolution. Each new discovery of this phenomenon weakens the evolutionary paradigm and strengthens the case for creation.


Evidence from Biogeography

Biogeography is the study of how and why organisms live where they do. It provides more evidence for evolution. Let&rsquos consider the camel family as an example.

Biogeography of Camels: An Example

Today, the camel family includes different types of camels (Figure (PageIndex<6>)). All of today&rsquos camels are descended from the same camel ancestors. These ancestors lived in North America about a million years ago.

Early North American camels migrated to other places. Some went to East Asia via a land bridge during the last ice age. A few of them made it all the way to Africa. Others went to South America by crossing the Isthmus of Panama. Once camels reached these different places, they evolved independently. They evolved adaptations that suited them for the particular environment where they lived. Through natural selection, descendants of the original camel ancestors evolved the diversity they have today.

Figure (PageIndex<6>). Camel Migrations and Present-Day Variation. Members of the camel family now live in different parts of the world. Dromedary camels are found in Africa, Bactrian camels in Asia, and Llamas in South America. They differ from one another in a number of traits. However, they share basic similarities. This is because they all evolved from a common ancestor. What differences and similarities do you see?

Island Biogeography

The biogeography of islands yields some of the best evidence for evolution. Consider the birds called finches that Darwin studied on the Galápagos Islands (Figure (PageIndex<7>))). All of the finches probably descended from one bird that arrived on the islands from South America. Until the first bird arrived, there had never been birds on the islands. The first bird was a seed eater. It evolved into many finch species, each adapted for a different type of food. This is an example of adaptive radiation. This is the process by which a single species evolves into many new species to fill available ecological niches.

Figure (PageIndex<7>): Galápagos finches differ in beak size and shape, depending on the type of food they eat. Those eating buds and fruits have the largest beaks. Insect and grub eaters have narrower beaks

Eyewitnesses to Evolution

In the 1970s, biologists Peter and Rosemary Grant went to the Galápagos Islands to re-study Darwin&rsquos finches. They spent more than 30 years on the project, but their efforts paid off. They were able to observe evolution by natural selection actually taking place.

While the Grants were on the Galápagos, a drought occurred, so fewer seeds were available for finches to eat. Birds with smaller beaks could crack open and eat only the smaller seeds. Birds with bigger beaks could crack open and eat seeds of all sizes. As a result, many of the smaller-beaked birds died in the drought, whereas birds with bigger beaks survived and reproduced. As shown in Figure (PageIndex<8>), within 2 years, the average beak size in the finch population increased. In other words, evolution by natural selection had occurred.

Figure (PageIndex<8>). Evolution of Beak Size in Galápagos Finches. The left graph shows the beak sizes of the entire finch population studied by the Grants in 1976. The right graph shows the beak sizes of the survivors in 1978. In just 2 years, the mean beak size increased from about 9 mm to just above 10 mm.


How and why single cell organisms evolved into multicellular life

Gonium pectorale (photograph from the Volvocales Information Project by Aurora Nedelcu). Credit: The Volvocales Information Project by Aurora Nedelcu

Throughout the history of life on Earth, multicellular life evolved from single cells numerous times, but explaining how this happened is one of the major evolutionary puzzles of our time. However, scientists have now completed a study of the complete DNA of one of the most important model organisms, Gonium pectorale, a simple green algae that comprises only 16 cells.

This microscopic organism is helping to fill the evolutionary gap in our understanding. The two year research project was a global collaboration between Kansas State University, Universities of Arizona and Tokyo, and Wits University. It is documented in the prestigious journal Nature Communications.

Pierre Durand, a researcher in the department of Molecular Medicine and Haematology and the Evolutionary Studies Institute at Wits University is one of the project collaborators.

"The evolution from unicellular to multicellular life was a big deal. It changed the way the planet would be forever. From worms to insects, the dinosaurs, grasses, flowering plants, hadedas and humans, you just have to look around and see the extraordinary forms of multicellular existence," says Durand.

"It has been difficult to explain how this occurred because it was not an easy thing to have happened. So questions like 'why did single cells live together in groups at the very beginning of multicellularity when it puts them at a fitness disadvantage?' challenged us for a long time," says Durand. We still don't know most of the answers but this project has certainly filled one of the gaps in our current understanding.

There are many model systems for studying multicellularity but nothing quite like the volvocine green algae, the group to which G. pectorale belongs.

"The evolutionary transition to multicellularity has occurred numerous times in all domains of life, yet the evolutionary history of this transition is not well understood. However, the volvocine green algae include a diverse variety of unicellular, colonial, and multicellular species," says Durand.

There are many members of the volvocines with varying degrees of complexity, so it is possible to examine different stages on the road to multicellularity. The volvocines also evolved relatively recently (during the Triassic period about the time when the first dinosaurs appeared) and the mysteries of multicellularity are not lost in evolutionary time.

Reporting on the genome sequencing of Gonium pectorale, the scientists uncovered some of the genes that regulate cellular growth and division in this organism. This finding helps explain how single cells live together in groups - one of the earliest steps on the path to a multicellular existence.


Amazing Organisms and the Lessons They Can Teach Us

What do you have in common with rodents, birds, and reptiles? A lot more than you might think. These creatures have organs and body systems very similar to our own: a skeleton, digestive tract, brain, nervous system, heart, network of blood vessels, and more. Even so-called “simple” organisms such as insects and worms use essentially the same genetic and molecular pathways we do. Studying these organisms provides a deeper understanding of human biology in health and disease, and makes possible new ways to prevent, diagnose, and treat a wide range of conditions.

Historically, scientists have relied on a few key organisms, including bacteria, fruit flies, rats, and mice, to study the basic life processes that run bodily functions. In recent years, scientists have begun to add other organisms to their toolkits. Many of these newer research organisms are particularly well suited for a specific type of investigation. For example, the small, freshwater zebrafish grows quickly and has transparent embryos and see-through eggs, making it ideal for examining how organs develop. Organisms such as flatworms, salamanders, and sea urchins can regrow whole limbs, suggesting they hold clues about how to improve wound healing and tissue regeneration in humans.

Here are profiles of other amazing organisms that are entering the research world.

Australian Zebra Finch

Credit: Chris Olson.

Whether it’s a robin, sparrow, or yellow-rumped warbler, each songbird sings its own tunes. For decades, scientists have studied how the birds learn their unique songs. Many researchers, including Claudio Mello at the Oregon Health and Science University in Portland, study vocal learning in Australian zebra finches. These common birds sing a simple, easily analyzed tune. Mello and other scientists are identifying which genes and which parts of finch brains allow the birds to learn to sing their songs. Similar gene pathways and brain circuitry come into play when humans learn to speak. A better understanding of vocal learning in birds can shed light on how we acquire language and may help scientists and clinicians better address a broad range of speech and language disorders. For more information on finch-brain research, visit the NIGMS-funded ZEBrA website.

African Spiny Mice

Credit: Malcolm Maden, University of Florida.

If you’ve ever seriously cut or burned yourself, you probably ended up with a thick, stiff scar. Internal organs can be similarly scarred when damaged by a heart attack, car crash, or other trauma. Such scarring can make it hard for the organ to function and can even lead to death. Some scientists seeking ways to lessen or prevent dangerous scarring are beginning to study the African spiny mouse (Acomys kempi and Acomys percivali).

This mouse is the only mammal known to heal without scarring. Just like a lizard that can release then regrow a severed tail, the African spiny mouse can leave patches of its easily torn skin in a predator’s teeth, then regrow it later—healthy layers of skin that include hair follicles, sweat glands, fur, cartilage, blood vessels, and nerve fibers—all without any scar tissue.

Chelsey Simmons at the University of Florida in Gainesville studies cells from these mice to figure out how they do it. By contributing to the understanding of how and why scar tissue forms—or doesn’t form—this research could reveal ways to prevent scarring caused by heart attacks, severe burns, and other injuries.

Hawaiian Bobtail Squid

Credit: Dr. Satoshi Shibata.

Antibiotic medications are usually excellent at killing bacteria. But some types of bacteria protect themselves by joining together by the hundreds and sometimes thousands into a cooperative community called a biofilm. The biofilm helps bacteria evade antibiotics.

Biofilms are common in almost any moist, relatively undisturbed location (your mouth, shower stalls, wastewater treatment centers). They can be extremely difficult to destroy. Although they play an important role in degrading organic matter and pollutants, they can wreak havoc in the human body. They can block narrow passages in medical stents and other implants. They can also cause recurrent, life-threatening infections in lungs, intestines, and other organs.

Strawberry-sized Hawaiian bobtail squid, found in the shallow waters around Hawaii, give scientists a chance to study how biofilms form inside the body of a host animal. These miniature squid have a mutually beneficial relationship with a type of biofilm-forming bacteria. The squid nourish and cultivate their bacterial partners, which form a biofilm and wait on the surface of a special organ. When needed, the bacteria leave their biofilm and enter the organ, where they provide the squid with a sort of invisibility cloak, hiding it from predators.

Researchers such as Karen Visick at Loyola University in Chicago are studying this unique partnership between bobtail squid and their biofilm guests. They hope to gain a better understanding of how biofilms form, how they exist inside animals, and whether it’s possible to prevent, delay, or destroy them in humans.

Tasmanian Devil

Credit: iStock.

The Tasmanian devil, the world’s largest carnivorous marsupial, is in danger of extinction. In the past two decades, its population in the wild has plummeted by nearly 80 percent. One of the main causes is Tasmanian devil facial tumor disease. Animals with the disease develop tumors in and around their mouths. The tumors make it hard for the animals to eat, often leading to starvation.

The transmissible cancer is sweeping through Tasmanian devil populations. Researchers believe it spreads through the animals’ bite. When a healthy devil bites a diseased one, the resulting immune response leads to out-of-control cell growth and tumors. The disease kills more than 90 percent of animals that contract it.

Andrew Storfer at Washington State University in Pullman is studying genes from the tumors and from some of the few animals that have contracted and recovered from the disease. His work suggests that some devils survive because key elements of their immune systems have evolved to resist the cancer. These studies are helping with cancer research in humans and are particularly applicable to cervical cancer, another transmissible cancer. The work is also uncovering strategies to help prevent the spread of disease among Tasmanian devils in the wild.

Arctic Ground Squirrel

Credit: Brian Barnes.

Our brains need a steady supply of blood and nutrients. When that flow stops, such as during a heart attack or stroke, it can damage or kill brain cells. More cells are damaged when blood flow restarts.

This isn’t the case for hibernating animals. Animals such as the Arctic ground squirrel can lower their body temperatures, heart rates, and blood flow for weeks at a time. And when they stop hibernating, these levels come back to normal without causing any damage.

Brian Barnes and others at the University of Alaska in Fairbanks are studying these squirrels to see how their brains adapt to these changes, especially when their blood flow levels are low even when the squirrels aren’t hibernating. The work could help scientists learn new ways to prevent human brain damage that often occurs after a stroke.

Sea Lamprey

Credit: Jeramiah Smith.

Sea lampreys are parasitic fish that latch onto other fish using suction-type mouths. Lampreys then feed on the host’s blood and body fluids. Though harmful to other fish, these parasites have two traits that make them interesting research organisms. First, they can repair their spinal cords when injured, something most animals can’t do. Second, they’re able to streamline their DNA as they grow so that different cell types keep only the genes that are necessary to function and remove other genes that could be detrimental.

Lampreys were some of the first animals to evolve a backbone and other traits common to all vertebrates. Researchers are looking at this fish’s ancient genetic information to see what genes are essential in growing backbones and other characteristics, and how traits have been gained and lost along the way during evolution. Jeramiah Smith at the University of Kentucky in Lexington studies these lost traits in hopes of finding new and unexpected ways of solving some of today’s most devastating human health problems, such as paralysis, cancer, and infertility.

Claudio Mello’s research is supported in part by NIGMS grant number IDeA Networks of Biomedical Research Excellence program and Jeramiah Smith’s work is supported by Share.


Primate Family Tree

Due to billions of years of evolution, humans share genes with all living organisms. The percentage of genes or DNA that organisms share records their similarities. We share more genes with organisms that are more closely related to us.

Humans belong to the biological group known as Primates, and are classified with the great apes, one of the major groups of the primate evolutionary tree. Besides similarities in anatomy and behavior, our close biological kinship with other primate species is indicated by DNA evidence. It confirms that our closest living biological relatives are chimpanzees and bonobos, with whom we share many traits. But we did not evolve directly from any primates living today.

DNA also shows that our species and chimpanzees diverged from a common ancestor species that lived between 8 and 6 million years ago. The last common ancestor of monkeys and apes lived about 25 million years ago.


Watch the video: Why arent apes evolving into humans any more? - Myths of Human Evolution (February 2023).