103 votes
Accepted

How could humans have interbred with Neanderthals if we're a different species?

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 ...
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102 votes

Is evolution a fact?

A tiny bit of terminology Fact In popular culture, the term fact means "something that is true". I would consider a theory as being the closest concept in science to what is called a fact in the ...
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  • 67.5k
75 votes
Accepted

Are humans the only species who drink milk as adults?

Good observation! Gene coding for the lactase Gene LCT Mammals have a gene (called LCT C/T-13910) coding for the lactase enzyme, a protein able to digest lactose. ...
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  • 67.5k
56 votes
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Does it make sense to classify all humans in a single species?

Actually, we not only consider that all human beings belong to the same species (Homo sapiens) but even that we belong to the same subspecies (Homo sapiens sapiens). So, does it really makes sense? ...
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51 votes
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How do we know the human species arose in Africa?

There are two big prongs of the out of Africa theory or whichever name you wish to call it. Prong the first: fossil evidence. There are lots of different kinds of protohuman fossils. Homo erectus/...
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  • 3,978
36 votes

Is evolution a fact?

A scientific fact is something that is true. A fact cannot be proven false. This is no different from the common usage of the word. However, in science, we often do not definitively know what is true. ...
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  • 2,472
35 votes

Are humans the only species who drink milk as adults?

The problem with this question is 1) wording and 2) access. "Drink" and "digest thoroughly" are two different things. The latter does not prohibit the former. It is only lactose that is not tolerated;...
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29 votes
Accepted

Are humans more adapted to "light mode" or "dark mode"?

A question that requires quite a lot of guts to ask on this site :) Nonetheless, and risking sparking a debate, there are a few arguments that spring to (my!) mind that can support the notion that we ...
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  • 51k
27 votes

Is evolution a fact?

Tl/dr: No, evolution is not a fact (unless your definition of fact defines evolution to be a fact, in which case it is a fact...). And if that phrase ruffles your feathers, it suggests you should ...
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  • 1,354
24 votes

Are humans the only species who drink milk as adults?

Just to point out an exception, adult cows sucking other cows' milk are not uncommon. At least, it's common enough to be a concern in dairy farms and for simple fixes to have been developed. The usual ...
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  • 586
23 votes

Is evolution a fact?

None of the answers so far have really provided much evidence, so here is a small sample of the peer-reviewed articles, based on genomic information that provides the facts that we know so far that ...
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  • 4,970
20 votes

How could humans have interbred with Neanderthals if we're a different species?

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 ...
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  • 4,970
20 votes
Accepted

Why do humans suffer anxiety when they view "Trypophobia trigger images"?

Trypophobia is not a recognised specific anxiety disorder (Washington Post). It is worth mentioning that anyone can have a phobia to anything, this is merely a question of whether many people ...
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  • 11.2k
17 votes

Is evolution a fact?

It is easily observed that populations of organisms change over time, both phenotypically and genetically. With some organisms we can observe this over a few days of observation; with others we can ...
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  • 14.1k
15 votes
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Why do we have five fingers?

I found an interesting article in Scientific American (Coates, 2005), and I quote part of it: The condition of having no more than five fingers or toes [...] probably evolved before the ...
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  • 51k
14 votes

How could humans have interbred with Neanderthals if we're a different species?

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 ...
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  • 14.1k
14 votes
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Why aren't there any transitional animals today?

Every species on the planet is "transitional" - this is because there is no ultimate or final species. Species branch out from one another, sometimes species go extinct, leaving gaps between the ...
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  • 16k
14 votes
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Why do humans grow taller than their ancestors?

A likely misunderstanding of yours Now we almost don't fight with other species Misunderstanding about selection As you will go through this course, you will understand why this sentence makes ...
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  • 67.5k
14 votes

Do all living humans literally descend from one ape?

Just 6 million years ago, a single female ape had two daughters. One became the ancestor of all chimpanzees, the other is our own grandmother. Short answer Whether or not the claim is true actually ...
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13 votes
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Why are the genomes of Humans 99.5% the same?

In a genome that is 3 billion base pairs, a difference of 0.5% works out to a difference of 15 million bases. When a single base change can change the amino acid sequence of a protein, that can add up ...
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  • 4,970
12 votes

Why do humans suffer anxiety when they view "Trypophobia trigger images"?

As someone who is very disgusted by this kind of image, I think it is a caused by an association with maladies like burns, infections, and especially parasites. It is difficult for me to even describe ...
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  • 129
12 votes

Are humans the only species who drink milk as adults?

Here is a bit of a tangential example, because it isn't milk from cows. There are some varieties of ants (Primarily the Leaf-cutter ant, if memory serves) which will collect, breed, feed, protect and "...
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  • 121
11 votes
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Have humans finished evolving?

Issue in your introduction I thought that massive changes among organisms are over long periods of time. Actually, some evolutionary events can happen on a very short time scale. A single mutation ...
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  • 67.5k
10 votes

Why are humans so variable in appearance

Because we as humans are really really good at picking up small differences in humans and really really bad at detecting them in anything else. Animals are often quite good at telling each other ...
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  • 13.1k
10 votes

Is the Lucy fossil really what scientists claim it is?

Per the comments, the actual paper seems pretty like a pretty straightforward operation of normal science: Somebody noticed something that looked off about one of the bones and decided they'd look ...
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  • 6,917
10 votes

Are humans more adapted to "light mode" or "dark mode"?

From experiments it seems you should better use dark mode if you want to prevent myopia: Using optical coherence tomography (OCT) in young human subjects, we found that the choroid, the heavily ...
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  • 201
9 votes

Why did humans evolved the scratch reflex?

With about 20 square feet of skin constantly exposed to potential irritation, itching must serve an important protective/defensive function. The "scratch reflex" (I'm not sure I would call it that) ...
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9 votes

Is evolution a fact?

I am not very happy with most of the answers here as they seem to be too ideologically motivated and not so much about scientific reasoning. So I decided to give it another try. ...
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  • 275
9 votes

Are humans the only species who drink milk as adults?

Pigs can. At least one milk, and milk derivates, producer around here used/uses their own pig farms to dispose of all byproducts of production, overdue products returned from stores, same day unused ...
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  • 91
9 votes
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Endogenous retroviral insertions as evidence for evolutionary relationships among primates

The Yohn et. al. (2005) paper (from Evan Eichler's lab) is describing a single type of endogenous retroviral element (loosely think of it as a 'species'), called PTERV1. They show that there were ...
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