The most exciting time of the year for college basketball fans is about to begin. The NCAA March Madness tournament officially kicks off tonight with Selection Sunday, where the bracket for this year’s games will be set.
We’ve had a solid day of almost nothing but Android P feature spotlights, but they’re still not finished. We legitimately weren’t expecting this many new things in this developer preview. On top of all of the features already discussed, Android P introduces a revised text selection popup, though it’s nothing groundbreaking.
left: Android 8.1 Oreo. right: Android P.
There are a couple of changes to this popup, the most noticeable of which is the fact that the buttons are no longer all capitalized.
Google’s recently released Material Design-focused redesign of YouTube for Apple TV didn’t sit well with many customers, this author included, so small wonder the company issued a small update Friday fixing some of the biggest complaints about the app…. Read the rest of this post here
A new version of Google Photos is out in the wild and it’s sporting a brand new text selection feature for those with access to Google Lens. A teardown of the APK also reveals that Photos isn’t too far from getting a powerful tool for removing obstructions and ghosting effects from images, and it may soon have a new ‘themed movie’ generator that does all of the hard work of picking out content for short personalized videos.
Human evolution can seem like a phenomenon of the distant past which applies only to our ancestors living millions of years ago. But human evolution is ongoing. To evolve simply means that mutations — the accidental changes to genes that happen normally in the process of copying DNA — are becoming more or less common in the population over time.
These changes can happen by chance, because the individuals who reproduced happened to carry a particular mutation somewhat more often than individuals who didn’t have children. They can also happen because of natural selection, when carriers of a specific mutation are better able to survive, reproduce, or tend to their family members — and therefore leave more descendants. Every biological adaptation, from the ability of humans to walk upright on two feet to flight in birds, ultimately traces back to natural selection acting on these minute changes, generation after generation.
So humans are definitely still evolving. The question is whether we are still adapting: are individuals who carry harmful mutations living less long, reproducing less — ultimately leaving fewer descendants? For instance, terrible eyesight may have been a major survival disadvantage living on the savanna, but with glasses and laser surgery, it’s unlikely to prevent people from living a long life today. How commonly then are mutations under selection in contemporary humans?
Long Time Scale Makes Evolution Hard to Study
Because adaptations involve tiny changes in the frequencies of mutations from generation to generation and their fortune plays out over tens to hundreds of thousands of years, they are incredibly hard to study directly — at least in long-lived organisms such as people.
So while there is overwhelming evidence for human evolution and unequivocal footprints of adaptation in the genome, rarely have scientists been able to directly observe natural selection operating in people. As a result, biologists still understand very little about the workings of natural selection in humans.
Indeed, one of the clearest footprints of a past adaptation in the human genome involves a mutation that permits milk to be digested in adulthood. This mutation in the lactase gene rapidly rose in frequency with the rise of dairy farming thousands of years ago, independently in multiple populations. It’s the reason some people can drink milk as adults, whereas most remain lactose intolerant.
But even in this well-studied case, let alone for the rest of the genome, researchers don’t know whether the mutation was beneficial for survival or for reproduction; whether the benefits were the same for both sexes, or across all ages; or whether the benefit depended on the environment (for instance, availability of other food sources). As pointed out by evolutionary biologist Richard Lewontin in the 1960s, to learn these properties of natural selection would require a massive study, in which genetic and genealogical information is obtained for hundreds of thousands of people.
Fifty years later, our group realized that this thought experiment is starting to become feasible. We sought large biomedical data sets that would let us learn about mutations that affect survival.
Looking at Gene Frequency Across Age Groups
Our basic idea was that mutations that lower the chance of survival should be present at lower frequency in older individuals. For example, if a mutation becomes harmful at the age of 60 years, people who carry it have a lower chance to survive past 60 — and the mutation should be less common among those who live longer than that.
We therefore looked for mutations that change in frequency with age among around 60,000 individuals from California (part of the GERA cohort) and around 150,000 from the U.K. Biobank. To avoid the complication that people whose ancestors lived in different places carry a somewhat different set of mutations, we focused on the largest group with shared ancestry within each study.
Across the genome, we found two variants that endanger survival. The first is a variant of the APOE gene, which is a well-known risk factor for Alzheimer’s disease. It drops in frequency beyond age 70. The second harmful variant we found is a mutation in the CHRNA3 gene. Associated with heavy smoking, this inherited mutation starts to decrease in frequency at middle age in men, because carriers of this mutation are less likely to survive longer.
Both deleterious variants only had an effect long after the typical ages of reproduction for both females and males. Biologists usually consider such mutations to not be under selection. After all, by late middle age, most people have already passed their genes on to whatever offspring they’ll have, so it seems like it might not matter how long they live beyond that point.
Why then would we only find two, when our study was large enough to detect any such variant, if common in the population? One possibility is that mutations that only imperil survival so late in life almost never arise. While that is possible, the genome is a large place, so that seems unlikely.
The other intriguing possibility is that natural selection prevents even late-acting variants from becoming common in the population by natural selection, if they have large enough effects. Why might that be? For one, men can father children in old age. Even if only a tiny fraction of them do so, it may be enough of an evolutionary fitness cost for selection to act on. Survival beyond the age of reproduction could also be beneficial for the survival of related individuals who carry the same mutations, most directly children. In other words, surviving past typical reproductive ages may be beneficial for humans after all.
Your Mutations do Influence Your Survival
In addition to examining one mutation at a time, we were also interested in considering sets of mutations that have all been shown to influence the same trait, and might have very subtle effects on survival individually. For example, researchers have identified approximately 700 common mutations that influence height, each contributing only millimeters. To this end, we considered tens to hundreds of mutations that shape variation in one of 42 traits.
We found genetic mutations linked to a number of diseases and metabolic traits that decrease survival rates: individuals who are genetically predisposed to have higher total cholesterol, LDL cholesterol, risk of heart disease, BMI, risk of asthma, or lower HDL cholesterol tend to die younger than others.
Perhaps more surprisingly, we discovered that people who carry mutations that delay puberty or the age at which they have their first child tend to live longer. It was known from epidemiological studies that early puberty is associated with adverse effects later in life such as cancer and obesity. Our results indicate some of that effect is probably due to heritable factors.
So humans carry common mutations that affect their survival and natural selection appears to act on at least a subset, in some contemporary environments. But what is bad in one context may well not be in another; as one example, the CHRNA3 variant has an effect because people smoke. These are early days, however, and our findings offer only a first glimpse of what can soon be gleaned from millions of genomes, in combination with genealogical records. In future work, it will be important to study not only lifespan, but also the number of children and grandchildren individuals leave, as well as populations and environments worldwide.
In a new paper published by Science, Alexey Kondrashov, Professor of Ecology and Evolutionary Biology at the University of Michigan, along with the co-authors of the study, have proposed that a discrepancy between the predicted amount mutations in a species and the actual number is explained by sexual intercourse compounding mutations. When mutations combine and interact, it expedites the time it takes for natural selection to work against negatively mutated individuals.
The study first calculated the theoretical mutation rate of humans and wild fruit flies. Then, it amassed data from around 2,000 people and around 300 flies, in order to ascertain the proportion of real-world individuals with mutations. They found that the real world ratio was far lower than the theoretical one.
Shamil Sunyaev, a co-director of the project, told Phys.Org that this lead them to believe that “natural selection against highly damaging genetic mutations is ongoing in humans, and that it is aided by synergistic interactions between different parts of the human genome.” Essentially, mutation does not work in isolation, but different mutations can impact and worsen each other.
Mashaal Sohail, lead author on the study, went on to state that “sex had to come about in a species such as our own to allow for more effective natural selection because the mutation rate is too high to sustain otherwise.” Sex is the mechanism through which we combine mutations and therefore speed up the rate at which these mutations are eliminated, as they are exposed to other mutations that increase their effect.
This phenomena is called synergistic (or narrowing) epistasis, and the researchers concluded that it is has a more positive evolutionary effect than asexual reproduction, as it allows an organism to eliminate multiple mutations — that are the result of sexual genome mixing — in the death of a single organism that is no longer able to reproduce — or even reach the reproductive stage — due to stacked mutations.
New Perspectives on Natural Selection and CRISPR
The implications of this study are twofold. First, it gives a causal mechanism that explains why humans continue to reproduce at such a rapid rate — a key question in the field of population genetics. According to the study, rapidly multiplying may in fact be an efficient means of mutation purging.
It also explains why there were fewer people and flies with lots of detrimental mutations. Natural selection continues to exert its influence in a world of effective medicine and adequate infrastructure.
The study, if it proves correct, would change the previous concept of genetic mutations, which saw them as manifesting and being purged on a micro level, with each being eliminated one by one.
This shift in perception towards a synergistic model has serious ramifications on the theories behind gene editing processes like CRISPR. CRISPR functions according to the logic of the micro alteration proposed above, making individual changes in the genome with the hope of altering one aspect or mutation.
Adobe has updated its Lightroom app for iPhone and iPad, with changes to the brush selection tool, in-app camera fixes, and support for the latest digital cameras and lenses. AppleInsider – Frontpage News
There were a number of small but interesting features of Android O (Oreo? Octopus??) that popped up at Google I/O back in May, and one of those was Smart Text Selection. I’m sure we’ve all been frustrated when trying to select text on our phones, and this feature intends to fix that by highlighting exactly what we need with a simple double tap. Now, Google Docs is implementing this feature and it should work for anybody currently running the Android O Beta.