Science questions not worth a thread I: I'm a moron!

[dutchfire]

You wanna do an experiment?
This (https://espace.cern.ch/be-dep/BEDepartmentalDocuments/BE/LHC_Schedule_2012.pdf) suggests "the Research Board" approves it. Whoever that is supposed to be.

 

[SS-18 ICBM]

I saw that, but it doesn't really go into too much detail. For all we know there's somebody dictating to the research board.

 

[Arakhor]

(6/49) * (5/48) * (4/47) * (3/46) * (2/45) * (1/44)

That's quite cool. I never thought of doing it that way. My scientific calculator automates it for me. [49 NCr 6]

 

[ace99]

Can someone explain what mitochondrial Eve and Y-chormosmal Adam are exactly, and what it means?

Also, Cracked had this article about human evolution: http://www.cracked.com/article_20078_5-weird-directions-human-evolution-could-have-taken.html

How much of that is actually true?

 

[Arakhor]

Mitochondrial-Eve and Y-chromosomal Adam are our most recent common ancestors, as in those two from whom every living human can trace some part of their genetic descent. They lived million years apart and were not our first ancestors, as genetic decay so far precludes us from finding even earlier ancestors.

Homo floresiensis really existed - at the time they were alive, archaeologists suggest that five different species of humans were living on this planet (Neanderthals, Denisovans, Flores Men, Cro-Magnons/Early Modern Humans and one other that I can't recall right now). Neanderthals would certainly have been different, but there's no way of proving their capabilities, as far as I know. It is also said that modern Europeans retain 1-4% of our DNA from Neanderthal ancestors, some 25-35,000 years ago.

Troodons may well have evolved into something unusual had the KT-Extinction occurred, but we'll never know for certain how they could have developed. The alien stuff I have no idea about.

 

[Eran of Arcadia]

Also, Cracked had this article about human evolution: http://www.cracked.com/article_20078_5-weird-directions-human-evolution-could-have-taken.html

How much of that is actually true?

Very little, at best.

 

[El_Machinae]

Homo floresiensis is one of my favorite stories. It really, really looks like some humans (Erectus?) shrank and lost brain power while on the island of Flores. Plus, it was so recently!

 

[hobbsyoyo]

Homo floresiensis is one of my favorite stories. It really, really looks like some humans (Erectus?) shrank and lost brain power while on the island of Flores. Plus, it was so recently!

It doesn't follow that they shrank and thus lost brain power. You can have a smaller brain with a smaller body mass and still be more intelligent. Consider that Neanderthals had bigger brains that we do, as elephants and whales.

 

[MCdread]

Can someone explain what mitochondrial Eve and Y-chormosmal Adam are exactly, and what it means?

Mitochondrial-Eve and Y-chromosomal Adam are our most recent common ancestors, as in those two from whom every living human can trace some part of their genetic descent. They lived million years apart and were not our first ancestors, as genetic decay so far precludes us from finding even earlier ancestors.

Mitochondrial Eve and Y-chromosome Adam are not our most common recent ancestors. They are, respectively, the most common recent ancestor of everyone's matrilineal line and everyone's patrilineal line, i.e., the most recent common ancestor of specific parts of our genome. Mitochondrial DNA is only inherited from our mothers, so mitochrondrial Eve is the most recent woman that is the ancestor of the mother of the mother of the mother, etc. of everyone alive today. Likewise, the Y chromosome is only transmitted by our fathers, so Y chromosomal Adam is the most recent father of the father of the father, etc. of all of us. They're estimated to have lived thousands (not millions) of years apart somewhere in East Africa (probably).
The most recent common ancestor of all humans alive today is estimated to have lived much more recently.

 

[Arakhor]

You got me on the thousands/millions part - that was just careless. I'm not seeing an awful lot of difference between "those two from whom every living human can trace some part of their genetic descent" and what you wrote.

 

[Meteor Man]

Yeah, you two pretty much said the same thing.

 

[emzie]

The correct answer is the literal couple described in the literal account of history, Genesis, Chapter 1.

 

[Mise]

"father of father of father... etc" is different from "common male ancestor". The common male ancestor of you and a cousin on your mother's side would be your mother's grandfather, but that wouldn't be the same as the father of your father. The "Y-chromosomal Adam" for you and your maternal cousin would be waaaaay back in your ancestry, depending on whether you lived in a tiny village in South America or in a big, well connected city like London or New York. But it wouldn't be your maternal grandparent.

Everyone in Europe can trace some part of their DNA to Henry VIII or something, but Henry VIII wouldn't be everyone in Europe's Y-chromasomal Adam. Having a common ancestor is quite, err, common, but having a common "father-of-father-of-father-of...etc" is a much more restrictive thing.

 

[MCdread]

You got me on the thousands/millions part - that was just careless. I'm not seeing an awful lot of difference between "those two from whom every living human can trace some part of their genetic descent" and what you wrote.

Yeah, you two pretty much said the same thing.

"father of father of father... etc" is different from "common male ancestor". The common male ancestor of you and a cousin on your mother's side would be your mother's grandfather, but that wouldn't be the same as the father of your father. The "Y-chromosomal Adam" for you and your maternal cousin would be waaaaay back in your ancestry, depending on whether you lived in a tiny village in South America or in a big, well connected city like London or New York. But it wouldn't be your maternal grandparent.

Everyone in Europe can trace some part of their DNA to Henry VIII or something, but Henry VIII wouldn't be everyone in Europe's Y-chromasomal Adam. Having a common ancestor is quite, err, common, but having a common "father-of-father-of-father-of...etc" is a much more restrictive thing.

It is as Mise said. "those two from whom every living human can trace some part of their genetic descent" would be the most recent common ancestor, not the mtDNA-Eve nor the Y-Adam. Mise's example of of two cousins explains the difference.

The mtDNA and the Y-chromosome are unique parts of the genome that do not recombine when two individuals mate and that's why they are important and used in deep genealogical studies. Every other bit of DNA randomly (not quite but let's assume so) mixes up and recombines, i.e., you get half of your genome from your father and half from your mother, but unless you have sequenced your parents' genome, you cannot know which bit of your DNA comes from whom. With the mtDNA and the Y chromosome you do. And you know they came from your maternal grandmother and your paternal grandfather respectively (and only them!). And so on, always on the matrilineal and patrilineal lines all the way back to the mtDNA Eve and Y Adam. When you model this pattern of transmission you end up with estimates of a hundred thousand years or more between now and the time those two individuals lived (but orders of magnitude less for the most recent common ancestor), because, as Mise said, we're asking a much more restrictive question.

Also, what did you mean by "They lived million years apart and were not our first ancestors, as genetic decay so far precludes us from finding even earlier ancestors."? Genetic decay as in DNA in fossils being slowly destroyed over time? If so, this has nothing to do with genetic decay. MtDNA Eve and Y Adam's age is estimated by reconstruction of a lineage tree based on samples of living people and a model of how many mutations genetic material accumulates in a given period of time on average.

 

[Arakhor]

I was under the impression that since DNA degenerates in fossils, it would be progressively harder to find earlier samples (or any at all). If I'm still wrong, that just shows I'm not a doctor and really don't understand this!

 

[MCdread]

I was under the impression that since DNA degenerates in fossils, it would be progressively harder to find earlier samples (or any at all). If I'm still wrong, that just shows I'm not a doctor and really don't understand this!

Sure, DNA progressively degrades in fossils (enzymes from the individual and from microbes (in the short term), as well as moisture (in the longer term) break the chemical bonds), but mtDNA Eve and Y-ch. Adam are not fossils (they may exist as fossils somewhere but even if we ever find them we have no hope of identifying them). They are putative individuals who have existed by definition (because everyone's mtDNA and Y chromosome have to converge to some "founding mother/father"), and whose age is estimated by a mathematical model based on mutation rates data.

Also, mtDNA Eve is the most common recent ancestor of mitochondrial DNA lineages that are currently alive, so the identity of Eve has changed (and became younger) throughout history as some lineages became extinct without leaving descendants. These conclusions are independent of fossil data (although fossil data may help us localising the regions were these events took place and constraining the models), but it's true we can, for example, sample egyptian mummies to see which mtDNA lineage did they belong to. And indeed, because DNA degrades, we wouldn't be able to do the same for older fossils.
So, your statement regarding degradation is correct. I just wanted to make sure you were not implying mtDNA Eve and Y Adam are archaeological specimens (but maybe I misinterpreted your post. ).

 

[SS-18 ICBM]

It doesn't follow that they shrank and thus lost brain power. You can have a smaller brain with a smaller body mass and still be more intelligent. Consider that Neanderthals had bigger brains that we do, as elephants and whales.

Below a certain size the loss of potential neural connections begins to affect brain power significantly. H. floresiensis has a small brain even for a chimpanzee.

 

[emzie]

Below a certain size the loss of potential neural connections begins to affect brain power significantly. H. floresiensis has a small brain even for a chimpanzee.

Yet controlled fire, cooked meat and had comparatively advanced tools?

 

[hobbsyoyo]

Below a certain size the loss of potential neural connections begins to affect brain power significantly. H. floresiensis has a small brain even for a chimpanzee.

Do we know how wrinkled it's brain was? IIRC, chimps have smooth cortexes, which makes a huge difference.

 

[PlutonianEmpire]

I vaguely recall, probably incorrectly, that there was a mass-computing project similar to Seti@home, where users' home computers analyze data in the background, looking for exoplanets or something. Is this recollection correct? Or did I get confused somewhere?