97

Short answer The concept of species is poorly defined and is often misleading. The concepts of lineage and clade / monophyletic group are much more helpful. IMO, the only usefulness of this poorly defined concept that is the "species" is to have a common vocabulary for naming lineages. Note that Homo neanderthalis is sometimes (although it is rare) called ...


19

The definition of species is open for debate, and this is especially the case when you try to define it from a paleontology perspective. Homo neanderthalensis was first discovered and defined in the 1860's, long before we were able to sequence their genome, which was published in 2010. There genome was different enough that most scientists would still say ...


18

Rice and Salt$^1$ bred fruit flies for 35 generations and from one line of flies created two groups that were isolated from each other reproductively. They could not interbreed because they no longer bred in the same environment. Depending on one's definition of 'species' this could be a case of artificial speciation. $^1$Rice WR, Salt GW (1988), Speciation ...


17

I am confused, can evolution ( speciation ) really occur in such a short time? Well, Evolution and Speciation are not the same. Evolution is the adaptation of an existing species to an environment over generations. Speciation is the development of a new species, and the definition of "species" can vary depending on who you talk to - but a very commonly ...


13

In addition to @Remi.b's answer on the species concept, and the perils of using human definitions to try to encompass biological reality, you need to understand what "interbreeding" meant to humans and neanderthals. Fertile crosses between sapiens and neandertalis were very rare, probably less than one successful cross per generation, and there's some ...


9

The hybridization situation you describe could be found in ring species, and is partially related to this concept. For instance, the three species A, B and C could have partially overlapping distributions, such as: In such a situation (assuming that the relative distributions have been stable over evolutionary time), A and C might be able to produce ...


8

Diane Dodd's experiments on Drosophila pseudoobscura would be another example of lab-based speciation. http://www.jstor.org/stable/2409365?__redirected To summarise - four populations each adapted to feeding on a starch-based diet and a maltose-based diet were evolved in the lab to test effects on mating preferences; compared to what is expected by random,...


8

This is a common misconception about evolution, many skeptics ask something along the lines of "If humans evolved from monkeys, why are there still monkeys?" The answer is that evolution is not a linear process of one species becoming the next species becoming the next. Species branch off much more like a tree. At some point in the past the last common ...


8

Evolution can occur in just one full generation Strong selection will rapidly reduce the gene frequencies of genes which cause negatively selected phenotypes. This reduces the likelihood of unfavourable genotypes occurring in the next generation. (I regard generation here as the complete cycle of one individual being born to the point at which they ...


8

I know that there are animals that are "simpler" than other animals but are there any that are half-evolved? Why aren't there living half ape and half humans? Oh come on. You know if Australopithecines or Homo habilis still existed you would be asking "Why aren't there living half Homo habilis and half humans"? And when the other Great Apes go extinct you'...


7

Well, what you seem to be suggesting is "Did life evolve twice on Earth?" Your original question has an answer: Probably yes. It's not unlikely to think that the original cell evolved into two different paths and then one went extinct. However, that doesn't address LUCA. If we found fossil evidence of what we thought was LUCA, and then fossil evidence that ...


7

How are such species are defined, and at what point dogs stop being dogs anymore? This is a bit like the is-Pluto-a-planet-discussion. A group of scientists have to come together and hold a big conference. You have a few principles that you want to adhere to and then it's big groups of people making decisions.


7

This is a very fundamental, and in my opinion, interesting question. You might not find many sources that directly cover this question because it is hard to test. If speciation did happen in two separate locations and the resulting species were so similar that they could breed with one another and not the original species, how would we be able to tell if the ...


6

There are many definitions of a species, which may or may not include the concept of reproductive barrier. The Biological Species Concept (BSC) is quite popular and involves a reproductive barrier, but other concepts such as the Phylogenetic Species Concept do not include a reproductive barrier. Disagreements and confusion also happen over just what the ...


6

Cats, dogs and bears all belong to the Carnivora clade of mammals, but they are not the only ones belonging to this clade. For instance, cats are more closely related to mongoose and hyenas than to dogs or bears, who in turn are more closely related to raccoons, weasels, and walruses. Their common ancestors likely displayed various adaptations to a ...


6

By definition, polyploidy just means that a cell or organism contains more than 2 pairs of homologous chromosomes (or is more than 2n). This is more common in plants than it is in animals. The plant, as shown below, undergoes failed meiosis, which means that the diploid (2n) cells never become haploid (n). As a result, a plant ends up with more than 2n when ...


6

Speciation in sexually-reproducing organisms can be identified as the inability to produce viable offspring. In other words, when two suspected sub-species are not able to produce viable offspring, they can be considered to be two species. In this case it is not so much determined at the molecular level, but at the organismal level. This mating procedure ...


6

Species are generally defined in terms of populations (see e.g. the wikipedia page), and it is therefore relatively meaningless to talk about individuals as species. That species is defined in terms of populations is true for many species concepts, e.g. as groups that can produce fertile offspring (biological species concept) or as a evolutionary distinct ...


6

There are a few issues your question brings up. First, the idea that species evolve from simple to complex is actually not a prediction or inevitable consequence of evolution by natural selection. The terms "simple" and "complex" themselves are ill-defined. For instance, if you defined "complex" to be size of the genome, the most complex organism found to ...


5

A commonly used empirical example of species selection (a.k.a clade selection, lineage selection) is pelagic larvae in sessile ocean species. See Maliska et al (2013) for a recent paper discussing this in Tunicata and Jablonski & Hunt (2006) for larval modes in gastropods. The idea is to some extent really intuitive - pelagic larvae means higher ...


5

As you probably know, there exists many different species concepts (or definitions of species). Often, you see a separation into at least six different categories of species concepts, which are then often subcategorized futher (and they can also overlap to some extent), namely: Biological species concept Phylogenetic/cladistic species concept Evolutionary ...


5

How has the theory of evolution changed over time? It improved quite a bit. To put things in perspective; today most of evolutionary biology is about evolutionary genetics while at Darwin time (On the Origin Of Species was published in 1859), we really had no idea about DNA (the basic structure of DNA was only discovered in the 1950s). A number of the ...


4

We can be reasonably certain that ALL species that exist today share a common ancestor, a common origin. Every single species we have even encountered, for example, uses a long chain of nucleotides (DNA or RNA1) to store its genetic information. If life had arisen through multiple independent sources, we would expect to find different solutions to the ...


4

Such examples are not that rare: multiple species are polymorphic for supernumerary (B-chromosomes), others are known to show intra-specific Robertsonian polymorphism (fusions of acrocentric/separation of metacentric chromosomes). One very well studied example, which covers both intra- and inter-specific crossings, are isopod crustaceans from the Jaera ...


4

You are mixing up two different things in your question: the mechanisms (processes) that cause micro- and macroevolution, and the genetic basis for different types of traits. The processes of evolution (selection & drift acting on genetic variation) are the same for both micro- and macroevolution, and this what the Wikipedia article is stating. The ...


4

yes it possible, in one article show a study for Mycoplasma genitalium which have 525 gene, however only 382 genes are essential for biological functions, they take out the nature gene and place the ' artifical gene' which synthsis in vitro, to test if the M. genitalium will survival when the No. of gene lower than 382. If it survival it will be a new ...


4

I offer this perspective in addition to what WYSIWYG has provided. Phylogenetic trees are tools to model what has actually happened, or what some evidence implies has happened, to a population of entities that exchange genetic material. These models fail, for instance, when describing the phenomenon of horizontal gene transfer since a tree is acyclic by ...


4

The term that describes this phenomenon is 'clinal speciation', and the easiest examples to point to are all 'ring species'. Wikipedia mentions four ring species examples. Three are avian examples (Larus gulls, Song Sparrows, and Greenish Warblers), and one is a plant example (Euphorbia tithymaloides). The classification of the Larus gull complex as a ring ...


4

Wow, interesting theoretical question. If scientists compared the parent's genes to the hatchling's genes and decided they're sufficiently different to merit their designation as distinct species, then I imagine they would give the young its own scientific name. But it's hard to imagine such an event happening. New species generally evolve gradually over ...


4

Absolutely it is possible for the current human species to evolve in to two distinct species in the future. Barriers to reproduction, such as physical isolation, help the process along as it allows differences to accumulate. Gene flow allows hybridisation (not in a species to species sense, but sub-population to sub-population sense) which will impede the ...


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