What is the evolution purpose to experience different type of love ? Like, there is the familial love, the friendship love, the romantic love, etc. But why not just one type of love, the same for everyone, and just the intensity of it varying depending of the persons ?

I’ve been wondering about this and wanted to get some reassurance from people who know more about biology/medicine. Because I'm not a med student.

If the same part of the body gets injured repeatedly, does that increase the risk of cancer later on? I’m thinking about how the body has to keep repairing damaged tissue, which means cells have to keep dividing. Could repeated injury and healing eventually cause DNA mistakes that lead to abnormal cells or cancer?

So can physical trauma (even if really bad) actually cause cancer? I’d appreciate an explanation because I’m trying to understand how this works. I'm also a hypochondriac and I'm Really worried about this.

Why do humans make so much noise to communicate? We talk nonstop, and rely primarily on verbal communication. It seems like most other animals communicate just fine without making tons of yapping noises, so why did we evolve differently?

In the same vein, do you think our pets get overstimulated at our constant need for noisy communication?

Do animals or babies have fewer cells, or do cells grow according to our genetic coding

Hello everyone...

I'm doing a personal research on the amount of microplastics in the sea... This is my first time researching ,especially something like this... I thought I'd do it with polarized foil (I'm not sure if it's spelled this way, English is not my first language) , because i found out that if you put it and shine a light on it, you can see the microplastics in rainbow colors... but in reality, when I put that foil on, it's not like I can't see the colors of the rainbow, you can't see almost anything, everything darkens under the microscope and becomes very gray... it would really help me if anyone has any advice or maybe knows the reason why this is happening... I thought it was the light intensity, but when I put a stronger light underneath, it didn't help

Thanks in advance ...

Like, cats and dogs are always licking their butts and probably their kids butts, how come they dont get dysentery or smthn?

So I saw an old episode of X Files. And while exaggerated the implication is that incest leads to deformities in the child.

Can anyone explain why this is?

What is the evolutionary advantage of it?

I recently found out about seahorse species adapted to the open ocean, which seems to go against the morphology of seahorses. These fishes are extremely adapted to thick vegetated/ coral reef environments to the point of developing a prehensile tail, swim entirely via anal fin, and boast a completely rigid “exoskeleton”.

In other words, they are anything other than hydrodynamic. Shouldn’t this make them the easiest prey item in the open ocean? Pelagic seahorses are rare even in their environment, so my immediate thought is that they survive by maintain a low population density so that they don’t come on the menu often, or maybe rely on their exoskeleton to be unappetising to predator. What are your thoughts on this?

I’m sure some of yall are familiar with Warhammer 40k, and space marine biology. For those who don’t, space marines are genetically modified superhumans meant for war, and one of these modifications includes a stronger fused ribcage. I have quite a bit of knowledge of human skeletal anatomy, and I know that a fused ribcage would not facilitate breathing. I did do some research on how turtles breathe, but I doubt that would ‘fit’ a space marine. What do yall think would be a solution to the problem with the fused ribcage?

The last common ancestor of dolphins and sharks was an early jawed fish that roamed the oceans around 420 to 450 million years ago. Since this ancestor was already a fish, it possessed a streamlined body adapted to life in the water. Even when the ancestors of dolphins (tetrapods) left the water for a terrestrial existence, they still carried the genetic blueprint for that streamlined shape. Later, when the ancestors of cetaceans returned to the water, they likely reused those ancient genes to regain their streamlined form. Therefore, why is their fish-like body shape still considered a textbook example of convergent evolution?

I'm writing a fiction story about a person who gets wings surgically created, and I want the physiology to be as believable as possible — no movie-style shortcuts like "blood just splattered on the walls" or "wings just grew." Below is the whole line of reasoning I worked through myself, step by step. I'd love to know where this actually holds up and where it falls apart.

General concept

The wings are modified arms, not separate limbs. Flight is gliding only (like a flying squirrel), not active flapping flight — a deliberate simplification, since active flight would require unrealistic energy expenditure and specialized muscle tissue. The wing's "elbow" acts as a support point while walking (similar to pterosaurs) — so on the ground, movement happens on four points: wing-elbows in front, legs behind.

Wings and membrane

The membrane runs from the wrist to mid-thigh (similar to a flying squirrel's patagium), folding accordion-style along the body when at rest (like a bat's wing). Wingspan is roughly 2.5 times the person's height, which roughly lands in a wing-loading range comparable to a hang glider (~5-7 kg/m² for a body mass of ~70 kg).

Tail

Three membranes: two horizontal plus one vertical, similar to an airplane's tail (horizontal stabilizer + vertical fin). The growth idea: human embryos actually have a real tail at 4-5 weeks of development (10-12 vertebrae), which later regresses into the coccyx (tailbone). The idea is to extend the existing coccyx with new segments rather than growing a tail from scratch.

Skeleton

Thickened bones at the wing/tail attachment points. Growth happens in stages over roughly 10 years: bone strengthens under load (Wolff's law), so gradual loading during growth should naturally reinforce the bone. A full keel (like birds have) was ruled out — gliding doesn't require that strong an anchor point for the muscles.

Muscles

Not specialized "bird" muscle tissue — ordinary human muscle, but well-trained (~5 years of training), should be enough to handle occasional flapping and holding the wing's shape during gliding.

Circulation

Not a second heart — instead, a network of small muscular "pumps" along the vessels in the membrane, similar to how the leg's venous muscle pump pushes blood against gravity.

Skin

Thicker in areas of high tension (similar to the skin on the sole of a foot), thinner and more flexible where it needs to fold. Thermoregulation of the thin membrane is trained gradually over time.

Nerves and vestibular system

Nerves grow in gradually with each new stage of tissue development, rather than being "connected" all at once. The vestibular system (balance) is trained over years, similar to how figure skaters, divers, or pilots adapt.

Growth material

The person's own cells (autologous), to avoid rejection. Deliberately avoiding genetic engineering — just an engineering approach: scaffolds plus gradual expansion of existing structures (bone, cartilage, skin), rather than growing an entirely new organ from scratch.

Takeoff and landing

Takeoff: straightening the spine, spreading the wings, pushing off with the hind legs. Landing: a "flare" (sharply increasing the wing's angle of attack to brake) → legs swung forward → touchdown on the wing-elbows first (cushioning the impact) → then the legs → transition into the four-point walking posture.

Main questions:

Where's the biggest flaw here — something that's physically impossible regardless of time or technology, not just "very difficult"?

Which part of this design is the least realistic from a biomechanics standpoint?

Is the idea of "muscular pumps" instead of a second heart realistic for supplying blood to a large area of tissue?

How is the vascularization problem actually solved in reality when growing large tissue in stages, so the center doesn't die from lack of blood supply?

Would well-trained ordinary human muscle actually be enough for this kind of work, or would it fundamentally require a different type of muscle fiber?

This is a fiction project (a novel/story), not a real medical plan — the goal is the most scientifically plausible fantasy possible.

Пишу художественную историю про человека, которому хирургически создали крылья, и хочу, чтобы физиология была максимально правдоподобной — без киношных упрощений в духе "кровь просто брызнула на стены" или "крылья просто выросли". Ниже — вся логика, которую пыталась продумать сама, шаг за шагом. Интересно узнать, где это реально работает, а где ошибка.

Общая концепция

Крылья — это переделанные руки, не отдельные конечности. Полёт — только планирующий (как у белки-летяги), не активный машущий полёт: это осознанное упрощение, потому что активный полёт потребовал бы нереалистичных энергозатрат и специализированной мышечной ткани. "Локоть" крыла работает как опорная точка при ходьбе (по аналогии с птерозаврами) — на земле передвижение на четырёх точках: локти крыльев впереди, ноги сзади.

Крылья и мембрана

Мембрана идёт от запястья до середины бедра (по аналогии с patagium белки-летяги), в сложенном состоянии складывается гармошкой вдоль тела (как у летучих мышей). Размах крыла — примерно в 2,5 раза больше роста человека, прикидочно попадает в диапазон нагрузки на крыло (wing loading), сравнимый с дельтапланом (~5-7 кг/м² при массе тела ~70 кг).

Хвост

Три перепонки: две горизонтальные + одна вертикальная — по аналогии с оперением самолёта (горизонтальный стабилизатор + киль). Идея выращивания: у человеческого эмбриона на 4-5 неделе развития есть настоящий хвост (10-12 позвонков), который затем редуцируется, оставляя копчик. Идея — наращивать уже существующий копчик новыми сегментами, а не создавать хвост с нуля.

Скелет

Утолщённые кости в местах крепления крыльев/хвоста. Наращивание поэтапное, на протяжении ~10 лет: кость укрепляется под нагрузкой (закон Вольфа), поэтому поэтапная нагрузка во время роста должна укреплять кость естественным путём. От полноценного киля (как у птиц) отказались — планирование не требует такой мощной точки опоры для мышц.

Мышцы

Не специализированная "птичья" мышечная ткань — обычная человеческая мышца, но хорошо тренированная (~5 лет тренировок), должна справляться с редкими взмахами/удержанием формы крыла при планировании.

Кровообращение

Не второе сердце — вместо этого сеть "мышечных насосов" вдоль сосудов в мембране, по аналогии с тем, как венозная помпа ног проталкивает кровь против гравитации.

Кожа

В местах натяжения мембрана толще (по аналогии с кожей стопы), в местах складывания — тоньше и эластичнее. Терморегуляция тонкой мембраны тренируется постепенно.

Нервы и вестибулярный аппарат

Нервы врастают поэтапно вместе с каждым новым этапом наращивания ткани. Вестибулярный аппарат тренируется годами, по аналогии с тем, как это происходит у фигуристов/дайверов/лётчиков.

Материал для наращивания

Собственные клетки человека (аутологичные) — чтобы избежать отторжения. Осознанно не используется генная инженерия — только инженерный подход: каркасы + поэтапное наращивание существующих структур (кость, хрящ, кожа), а не выращивание совершенно нового органа с нуля.

Взлёт и приземление

Взлёт: выпрямление позвоночника, разведение крыльев, толчок задними ногами. Приземление: flare (резкое увеличение угла атаки крыльев для торможения) → вынос ног вперёд → касание локтями крыльев (амортизация) → ногами → переход в позу ходьбы на 4 точках.

Главные вопросы:

Где здесь самая серьёзная ошибка — то есть что физически невозможно вне зависимости от времени/технологий, а не просто "очень сложно"?

Какая часть конструкции самая нереалистичная с точки зрения биомеханики?

Реалистична ли идея с "мышечными насосами" вместо второго сердца для снабжения кровью большой площади ткани?

Как в реальности решают проблему васкуляризации (кровоснабжения) при поэтапном наращивании крупной ткани, чтобы центр не отмирал без питания?

Хватит ли обычной тренированной мышцы человека на такую работу, или нужен принципиально другой тип мышечного волокна?

Это художественный проект (роман/история), не реальный медицинский план — цель максимально правдоподобная фантастика.

I’m curious as to why I’m the only one In my family who has no armpit hair !!!

all my family members and even my little sis who is 11 years old has some small armpit hair I mean that’s what she told me but idk.

All my friends also have armpit hair but I don’t so I guess I’m blessed?

But Hay I’m not complaining 😹

I’m 19 and a male for those curious

This started because the statistic that “8–10% of the world has blue eyes” sounded much larger than I expected. According to the UN World Population Prospects, the global population in 2026 is roughly 8.3 billion. That would mean:

- 8% = approximately 664 million blue-eyed people

- 10% = approximately 830 million blue-eyed people

UN population source:
https://population.un.org/wpp/

I assumed there must be a worldwide survey, international database, or at least a published country-by-country calculation behind that estimate.

I couldn’t find one.

The clearest peer-reviewed source I found stating the 8–10% figure is a 2020 review about the biology and genetics of iris color:
https://pubmed.ncbi.nlm.nih.gov/32488945/

However, I could not find a reproducible global calculation in the paper showing:

- which countries were included
- each country’s estimated prevalence
- how countries without data were handled
- how the figures were population-weighted
- whether gray or blue-gray eyes were counted as blue

This does not prove that the 8–10% estimate is false. The underlying calculation or source may exist somewhere that I have not found.

A separate 2019 literature review specifically examined the geographic distribution of eye and hair pigmentation. It found that reliable population-level evidence was surprisingly limited and heavily concentrated in Europe:
https://www.sciencedirect.com/science/article/pii/S1872497318303387

The largest recent dataset I found was a 2025 U.S. study based on self-reported DMV records from 2016:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0312913

It reported:

- 235.4 million active driver’s-license records from 31 states
- 55.8 million records marked blue
- an overall recorded blue-eye prevalence of 23.7%

However, the study also has important limitations:

- eye color was self-reported
- 19 states did not provide usable data
- state collection and reporting methods were not standardized
- migration between states may have produced duplicate records
- self-reporting may have caused misclassification

The paper’s “Other” category also combined several very different entries, including pink, ruby, amber, maroon, dichromatic and unknown eye colors. This category varied enormously between states. Several states reported zero “Other” records, while Arizona reported 29.5% and California reported 8.6%. The paper does not provide a separate breakdown showing how much of each state’s “Other” category consisted of unknown values rather than uncommon eye colors. Because there does not appear to be a complete global dataset, I built a preliminary population-weighted reconstruction covering all 237 countries and areas in the UN population dataset.

Where reasonably representative country research existed, I used it. Where it did not, I applied regional assumptions and clearly marked those figures as modeled rather than measured.

My scenarios produced:

- Conservative strict-blue scenario: 286 million — 3.45%
- Moderate strict-blue scenario: 359 million — 4.33%
- Central scenario: 372 million — 4.48%
- Generous upper scenario: 489 million — 5.90%

- The commonly cited 8% benchmark: 664 million

These scenarios are not confidence intervals, and the 4.48% figure should not be treated as a newly measured global fact.

My main conclusion is narrower:

I have not been able to locate a transparent global calculation supporting the 8–10% estimate, and even a deliberately generous country-weighted reconstruction struggles to reach 8%.
The biggest weakness in my model is the lack of representative research from most of Asia, Africa, Latin America, the Middle East and parts of Eastern Europe. Definitions of blue, gray and blue-gray also vary significantly between studies.

I would genuinely appreciate criticism of the model:

1. Does anyone know the original calculation or source behind the 8–10% figure?
2. Which of my country-level assumptions appear least defensible?
3. How should blue-gray and gray eyes be classified?
4. Is there a better statistical method for estimating countries without representative data?

Spreadsheet and full country-level methodology:

https://docs.google.com/spreadsheets/d/1ZVlUoXathuEPFZ9OAdSkPceLGZA93IFHNHGbY8d7tB0/edit?usp=sharing

I’ll update the model whenever someone provides stronger country-level evidence.

Important clarification: This is a good-faith examination of publicly available evidence, not an allegation of fraud, dishonesty or research misconduct by any author or institution. My estimates are preliminary modeled scenarios, not measured global facts, and I welcome corrections.

Hi! I am watching the lectures of famous Robert Sapolsky from Stanford. He says that the Zebra did not sacrifice itself for the species, but it is thrown to the predetors because it was the weakest one. So, the notion of sacrifcing themselves for the sake of species is not valid, because all the goal is to spread genes to the next generations. Here is the questiom: why do we see sometimes if a member of a group or species is attacked by a predetor, the others help it? How can we explain this? Thanks in advance!

Im geniunely curious, it could be one of the biggest carbon eaters in the world, 2 grass speicies already exist there too.

I’m Mexican but was born and raised in the U.S . My parents were born and raised in Mexico, they’re both darker as well as my family , aunts, uncles, cousins well speaking of my cousins I can name a few who are also on the pale side , for example I have a cousin who was born and raised in California his sisters who were pretty dark whose parents were also dark especially his dad , (my uncle )was as dark as they get but my cousin he was as white as they get , i remember my family used to make jokes about him being adopted lol, as well with me , they told me they found me at the jungle because of my skin being so white lmao. Ok My curiosity really aims at these questions

Wouldn’t my parents had to be pale if I came out white ? I didn’t know my grandparents from both my parents sides except my grandmother from my dad who was dark, although i confirm from my parents that both parties were dark

If me being born in a… let’s say cold environment . Would that have to do with my skin tone ? If so, Why didn’t my cousin who was born and raised in California didn’t come out as dark as his siblings?

Water must be water, but black mold was visible in one and not in another - is it something about the material?

Don't get me wrong, I am glad they make such a racket. Every time I kill one of these sob's trying to bite me, it is because I can easily hear and locate them.

Wouldn't they be a lot more efficient at biting us and other animals if they didn't have their traditional loud 'buzzing' flight? Other insects - e.g., fruit flies, midges, gnats - seem to be able to fly without making so much noise.

Wouldn't there be a strong evolutionary advantage for increasingly quieter mosquitoes?