Are humans evolving faster or slower?

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Dream of Freedom
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Are humans evolving faster or slower?

Post by Dream of Freedom » Sat Jun 22, 2019 12:09 pm

Are we evolving faster or slower than prehistoric man? Certainly more of us make it through childhood and therefore have a better chance of reproducing. So the poorly adapted don't get weeded out as often. On the other hand, our population is far greater. More copies means more mutations.

Jason
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Re: Are humans evolving faster or slower?

Post by Jason » Sat Jun 22, 2019 2:12 pm

Based on my recent trip to Staten Island, I'm going with slower.

TheWanderingScholar
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Re: Are humans evolving faster or slower?

Post by TheWanderingScholar » Sat Jun 22, 2019 2:32 pm

Same rate, or a little bit slower as the environment we live is much more pleasant than 10k BC, at the beginning on the neolithic era, let alone when humanity still lived in the cradle.

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unemployable
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Re: Are humans evolving faster or slower?

Post by unemployable » Sat Jun 22, 2019 4:12 pm

Faster. The Stone Age lasted some three million years. That's about ten thousand times as long as the US has been a country.

intellectualpersuit
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Re: Are humans evolving faster or slower?

Post by intellectualpersuit » Sat Jun 22, 2019 5:18 pm

Faster. The environment has increased in complexity requiring more adaptation -> evolution.

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Lemur
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Re: Are humans evolving faster or slower?

Post by Lemur » Sat Jun 22, 2019 7:01 pm

Faster...gene editing can artificially speed this up.

daylen
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Re: Are humans evolving faster or slower?

Post by daylen » Sat Jun 22, 2019 7:07 pm

No simple answer. Measurement too sensitive to intergenerational variation. Complexity can be outsourced to neuroplasticity or higher-order social organization.

bigato
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Re: Are humans evolving faster or slower?

Post by bigato » Sat Jun 22, 2019 8:06 pm

Evolution is not improvement, it is adaptation for survival. In that sense, we are changing as fast as required by the environment so far and there's no reason why it would be any different. Proof of that is that we are alive as a species. So the question that matters is whether the environment is changing faster or slower, since evolution is driven by that. Now the changes in the environment coming ahead may be faster and more challenging than everything else homo sapiens has seen before.

bigato
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Re: Are humans evolving faster or slower?

Post by bigato » Sat Jun 22, 2019 8:08 pm

Also you need to clarify what exactly you meant by evolving, since in a specie so social and intelectual as ours, culture and education can be more relevant to survival than say, resistance to cold or hot temperatures.

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Ego
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Re: Are humans evolving faster or slower?

Post by Ego » Sun Jun 23, 2019 12:44 am

Off the top of my head it has to be faster for two reasons.

1. As population increases there are more people in general producing more variation.
2. Mobility allows dissimilar humans to reproduce which creates more variation. Think Edge Effect in ecology.

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Re: Are humans evolving faster or slower?

Post by jacob » Sun Jun 23, 2019 8:31 am


Kriegsspiel
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Re: Are humans evolving faster or slower?

Post by Kriegsspiel » Sun Jun 23, 2019 4:25 pm

The 10,000 Year Explosion also deals with evolution and where it's sped up.

Sclass
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Re: Are humans evolving faster or slower?

Post by Sclass » Sun Jun 23, 2019 7:14 pm

Interesting question. Mutation rate must undoubtedly be higher now than in the past. Toxins, ionizing radiation. Less ozone layer. Yet selection for good and bad mutation may be skewed by technology and society.

Selective pressure may not be as high as it was in the past. We have kind of the Idiocracy effect going on where dopey people can get easy food and reproduce. When resources are scarce you have to be pretty badass to breed let alone survive.

I don’t have a good understanding of evolutionary biology. Do we get higher evolution rates when we kill off life forms fast like using antibiotics on tuberculosis? Or do we get more evolution if we let things live and breed unrestrained? Some good mutations can possibly get killed off during lean times. I’m sure this is all figured out.

Augustus
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Re: Are humans evolving faster or slower?

Post by Augustus » Sun Jun 23, 2019 8:48 pm

What do you mean by evolving? We're evolving in the sense that we are mutating. That doesn't imply we're getting more intelligent or other traits that we find appealing.

Brains matter as much as noses to evolution, if a nose leads to more food and offspring than a brain, the nose is superior.

daylen
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Re: Are humans evolving faster or slower?

Post by daylen » Sun Jun 23, 2019 10:01 pm

It's complicated and difficult to measure. The mathematics behind evolutionary biology tends to make simplifying assumptions and/or focus on data limited to a particular level of selection. Contrary to popular believe, it is testable and can be coded into a mathematical framework, but there is a trade-off between rigorously formalizing genetic mechanisms and accounting for phenotypical/environmental factors.

A relevant Wikipedia article elaborates on this confusion:
https://en.wikipedia.org/wiki/Adaptive_ ... man_genome

"..it is clear that the debate over the amount of adaptive evolution occurring in human coding DNA is not yet resolved."

"The generally low estimates of adaptive evolution in human coding DNA can be contrasted with other species. Bakewell et al. (2007) found more evidence of adaptive evolution in chimpanzees than humans, with 1.7% of chimpanzee genes showing evidence of adaptive evolution (compared with the 1.1% estimate for humans; see Table 1)."

"Generally, there does appear to be a positive correlation between (effective) population size of the species, and amount of adaptive evolution occurring in the coding DNA regions. This may be because random genetic drift becomes less powerful at altering allele frequencies, compared to natural selection, as population size increases."

Consider the complexity of an ant. Studying the genetics and physiology of a single ant is not enough to infer its behavior when immersed in a colony. It is possible that humans evolved to decrease the complexity of our coding DNA in favor of a frontal lobe that improves learning ability (pardon the teleological phrasing). Continuously variable traits may not be additive towards an increase in the information entropy of our genome (*). Accounting for all the variables is not feasible, therefore non-linear relations between various levels of selection could potentially break any argument.

(*) I am shooting in the dark here, but I am not sure there is any other statistically valid way to quantify change in adaptive evolution at the scale of an entire species. The functional relationship between genotype and phenotype is not as trivial as tracking co-variations within a somewhat arbitrary classification scheme.

Toska2
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Re: Are humans evolving faster or slower?

Post by Toska2 » Sun Jun 23, 2019 10:25 pm

How can you parse epigenetics with evolution?
Hasn't travel/interbreeding create a homogenizing effect of genes, like chocolate milk?

I would say faster but not in the way the earth is. We control our environment and so we adapt to that. Humans live in clean apartments with allergies and glasses.

daylen
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Re: Are humans evolving faster or slower?

Post by daylen » Mon Jun 24, 2019 3:26 pm

@Toska2 Evolution occurs at many different scales via natural selection, mutation, and replication. DNA is a highly robust structure for encoding information about the development and reproduction of organisms. The genotype of an organism is a convenient data structure to work with when analyzing such information, and the phenotype of an organism includes all other observable characteristics. One of the major objectives of modern biology is to draw a detailed genotype-phenotype-environment map for all of Earth's inhabitants. Epigenetics is concerned with heritable changes in phenotype where the genotype is held constant. The majority of epigenetic research appears to be focused on more immediate levels emergent from the genotype such as gene expression and transcription.

Just as genes can mutate, epigenes can epimutate. Epimutation is more readily reversible and may serve as safe way to test new adaptations. If genes are hardware and memes are software, then epigenes are firmware.

So the question of what we mean by adaptive evolution depends what low-level changes are being linked to high-level changes. Genetic evolution takes a long time and is most apparent in fossil records where species appear static apart from rare occurrences of speciation (this is related to punctuated equilibrium theory). In absence of differential fitness, genetic drift is strong, and natural selection is weak (diluted in inter-generational variation/mutation). Epigenetic evolution occurs on a shorter time-scale and perhaps even during the course of a single lifetime. Cultural evolution is even more rapid, and perhaps this is partially why the frontal lobe requires 25 years to mature (to insure a more uniform sampling of the underlying culture).

Even with modern transportation infrastructure, genes do not travel nearly as quickly as memes. I do not think that modern society will last long enough to see a genetic melting pot (+). We are in a memetic melting pot. :)

(+) Too much homogenization may not be stable. Perhaps group selection favors individuals specializing in about 16 patterns of attention based on genetic predispositions. A highly controversial thought. This could also just be an emergent phenomenon dominated by a lower level.

daylen
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Re: Are humans evolving faster or slower?

Post by daylen » Mon Jun 24, 2019 5:55 pm

To further complicate this matter, there is debate about the validity of Lamarckian inheritance. Certain barriers may exist in biological processes that make information transfer one-way (irreversible), so acquired characteristics during the course of a single lifetime may not be recoded into the genotype to be inherited by offspring. The Weismann barrier, for instance, only allows the flow of heritable information from germline cells to somatic cells. Also, the "central dogma of molecular biology" is that no sequential information can travel from proteins to DNA or RNA. These views fit well with gene-dominated selection.

In addition, horizontal gene transfer recognizes another transmission vector between cells/organisms. A related topic in this realm is the hologenome where the genome of an organism is coupled to the community of symbiotic microbes taking refuge in the body.

A synthesis between evolution and complexity blurs the line between levels of selection and what forms should be focal. Information itself is a way of coding how something repeats conditionally (whether that is a gene, shape, symbol, time interval, object, etc.), and complexity is a measure of the encoding size. Generally, in physics, information processing is reversible, but more work tends to be required for agents to recover information when moving forward in time. Higher-order scientific models must assume that some information is lost (a shift to stochastic as opposed to deterministic processes). We are fundamentally limited by scarce attention, so the patterns of selection we focus on may be misleading.

7Wannabe5
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Re: Are humans evolving faster or slower?

Post by 7Wannabe5 » Thu Jun 27, 2019 1:16 pm

What daylen said.

OTOH, there is some anecdotal reporting of possibility of hybridization attempts in the late 1970s.


https://www.youtube.com/watch?v=7DKpAexJBJw

George the original one
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Re: Are humans evolving faster or slower?

Post by George the original one » Thu Jun 27, 2019 3:29 pm

Slower, because in the Darwinian sense, we're keeping more people alive that normally would have died. Thus no selection of the fittest.

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