Why Intercast marriages are discouraged

 

The following is just one example of what following a specific way of living does to us at a core genetic level all of history and all of our ways of living from the past we can delve into it but evolved around genetics, there is the reason why

The following is the response from Perplexity research to the question of how vegetarians have a special gene mutation that allows them to produce their own omega-3. 

How is this connected to Intercast marriages?? It’s for you to think it through an extrapolate from here. Extrapolation being the keyword. I will extrapolate for you later when I have more time. Until then, it’s for you to think. 

Yes, that Business Insider article is real and covers a fascinating piece of genetic science. Here's the full picture:

## The "Vegetarian Gene" — FADS1 & FADS2

The article you're recalling was based on a **2016 Cornell University study** published in *Molecular Biology and Evolution*. Researchers found a genetic variant — specifically a mutation called **rs66698963** — in the **FADS2 gene**, which also regulates the expression of **FADS1**. These two genes encode enzymes that are critical for converting short-chain plant-based omega-3 and omega-6 fatty acids (like ALA) into the long-chain forms the body actually needs — **EPA and DHA**.[1][2]

## How the Adaptation Works

Normally, the human body is quite poor at converting ALA (found in flaxseeds, walnuts, etc.) into EPA and DHA. But the **vegetarian allele** carries a 22-base DNA insertion that ramps up the activity of FADS1 and FADS2 enzymes, making the conversion process significantly more efficient. People with this variant can essentially synthesize sufficient EPA and DHA from plant foods alone, without needing fish or supplements.[3][4][5]

## Who Carries It

The variant evolved over **hundreds of generations** in populations with historically plant-based diets. The prevalence breakdown is striking:[4][6][1]

| Population | Frequency of Vegetarian Allele |

|---|---|

| South Asians (e.g., India) | ~70% |

| Africans | ~53% |

| East Asians | ~29% |

| Europeans | ~17% |

This makes sense — Indians, for example, have had large vegetarian populations for thousands of years due to cultural and religious practices, creating strong evolutionary selection pressure for this allele.[2]

## The Flip Side

Interestingly, the **Inuit of Greenland** evolved the *opposite* allele — optimized for a seafood-heavy diet. This shows that FADS gene variants have been shaped in both directions based on dietary environment. There's also a cautionary note: people with the vegetarian allele who then eat lots of **processed vegetable oils** (high in linoleic acid) may actually overproduce arachidonic acid, a pro-inflammatory compound — which was the nuance that some media coverage at the time got wrong.[7][1]

Given your background tracking Indian markets and your travel between the US and India, you likely fall into the demographic where this allele is quite prevalent — around a 70% chance if your ancestry is South Asian.

Sources

[1] Eating green could be in your genes | Cornell Chronicle https://news.cornell.edu/stories/2016/03/eating-green-could-be-your-genes

[2] Are We What We Eat? Evidence of a Vegetarian Diet Permanently ... https://academic.oup.com/mbe/article/33/7/1887/2579296

[3] Omega‐3 polyunsaturated fatty acids and vegetarian diets https://onlinelibrary.wiley.com/doi/full/10.5694/mja11.11507

[4] » The vegetarian gene: do you have super omega-3 ... https://hub.geneplanet.com/en/you-might-be-carrying-a-vegetarian-gene/

[5] A Vegetarian Diet Could Cause Long-Term Genetic Changes https://www.sciencealert.com/vegetarian-diets-could-cause-long-term-gene-changes-research-shows

[6] Vegetarian Diet Is Changing Human Genes - Business Insider https://www.businessinsider.com/vegetarian-diet-ichanging-human-genes-2016-4

[7] Being a vegetarian can kill you? How the press mashed a genetics story https://geneticliteracyproject.org/2016/04/04/vegetarian-can-kill-press-mashed-genetics-story/

[8] Switching between vegetarianism and non-vegetarianism? https://www.xcode.life/dna-and-nutrition/switching-vegetarianism-non-vegetarianism-must-read-first/

[9] Alpha-Linolenic and Linoleic Fatty Acids in the Vegan Diet https://pmc.ncbi.nlm.nih.gov/articles/PMC6835948/

[10] Southampton research shows plants could replace fish as ... https://www.southampton.ac.uk/news/2019/04/plant-oil-omega-3.page

[11] Achieving optimal n–3 fatty acid status: the vegetarian's ... https://www.sciencedirect.com/science/article/pii/S0002916523048955

[12] New-Onset Vegetarian Diet Shows Differences in Fatty Acid ... https://pmc.ncbi.nlm.nih.gov/articles/PMC10317312/

[13] Bioavailability and conversion of plant based sources ... https://pubmed.ncbi.nlm.nih.gov/33576691/

[14] Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications - PubMed https://pubmed.ncbi.nlm.nih.gov/12936959/?trk=article-ssr-frontend-pulse_little-text-block

[15] Major study suggests that vegans must supplement Omega ... https://www.reddit.com/r/vegan/comments/1glfyq3/major_study_suggests_that_vegans_must_supplement/

This is one of the most fascinating stories in all of evolutionary biology. Let me walk you through exactly how it works.

## Step 1: The Original Random Mutation

It starts with a **copying error**. Every time a human cell divides, about 3 billion base pairs of DNA get copied. Occasionally the cellular machinery makes a mistake — it inserts, deletes, or swaps a letter in the genetic code. Most of these errors are harmless, many are harmful, and very rarely one is *beneficial*. In this case, at some point deep in human prehistory, one person's DNA got an **extra 22-letter insertion** in the FADS2 gene — purely by accident. That one person became the origin point of the entire lineage.[4]

## Step 2: Natural Selection Decides What Happens Next

Here's the key: a random mutation doesn't spread on its own — **survival and reproduction spread it**. The process is called **positive selection**, and it works through a brutally simple logic:[1]

- If you carry a mutation that helps you survive and reproduce *more* than your peers, your children inherit it

- Your children outcompete others, have more children themselves

- Over hundreds of generations, what started as one person's random copying error becomes the majority genetic profile of an entire population[5]

For the FADS2 insertion, the selection pressure was stark: in a population eating primarily plants, **people who could efficiently synthesize EPA, DHA, and arachidonic acid from plant sources were healthier** — better brain development, better immune function, better reproductive outcomes — than those who couldn't. They had more surviving children. Those children passed it on. Repeat for 10,000+ years.[3]

## Step 3: The Timeline — It Goes Back to Neanderthals

The mutation is ancient. Researchers checked chimpanzee and orangutan genomes — the allele is **absent** in both. But strikingly, evidence of the vegetarian allele was found in **Neanderthal and Denisovan genomes**, meaning this mutation predates modern *Homo sapiens* entirely and is at least 40,000–100,000 years old. It may have arisen multiple times independently, or been inherited from archaic human ancestors through interbreeding.[4]

The FADS cluster also shows strong positive selection signatures **coinciding with the Agricultural Revolution** (~10,000 years ago), when populations across South Asia and Africa shifted from hunting to farming and animal food sources became scarcer.[7][8]

## Step 4: Why It Spread in India Specifically

India had a unique convergence of forces:[1]

- **Agricultural shift** removing reliable animal-based EPA/DHA from the diet

- **Religious and cultural vegetarianism** (Hinduism, Jainism, Buddhism) reinforcing plant-based diets for thousands of years

- **Consistent multi-generational selection pressure** — not just decades but literally millennia of vegetarian diets creating a sustained evolutionary filter

Each generation, people with the insertion allele were slightly healthier and had slightly more surviving children. That small reproductive advantage, multiplied across hundreds of generations, pushed the allele from a rare random mutation to ~70% prevalence in South Asian populations today.[4]

## The Profound Implication

What this means is that your genome is essentially a **diary of what your ancestors ate**. The mutation didn't happen because your ancestors *decided* to be vegetarian — it spread because vegetarianism created an environment where that accidental copying error happened to be the right tool for survival. Your DNA is literally shaped by thousands of years of cultural and dietary choices made by people you'll never meet.[3]

The flip side — and this is humbling — is that **evolution has no foresight**. It optimized your ancestors for a world of mustard greens, lentils, and ghee. It had no way to anticipate sunflower oil, processed food, or a Western diet. The gene that was a survival advantage for 10,000 years becomes a liability the moment the dietary environment shifts — which is exactly the situation millions of South Asian immigrants face today.

Sources

[1] Are We What We Eat? Evidence of a Vegetarian Diet Permanently ... https://academic.oup.com/mbe/article/33/7/1887/2579296

[2] Vegetarian Diet Driving Evolution? [IMAGE] - EurekAlert! https://www.eurekalert.org/multimedia/613389

[3] The “FADS2” diet: How vegetarian populations have different ... https://misciwriters.com/2016/06/28/the-fads2-diet-how-vegetarian-populations-have-different-genomes/

[4] Vegetarian populations carry metabolic mutation | PET https://www.progress.org.uk/vegetarian-populations-carry-metabolic-mutation/

[5] Genetics of the vegetarian diet FADS - Pillcheck https://www.pillcheck.ca/2016/05/13/genetics-vegetarian-diet-fads/

[6] Positive Selection on a Regulatory Insertion–Deletion Polymorphism ... https://pmc.ncbi.nlm.nih.gov/articles/PMC4915354/

[7] FADS1 and the Timing of Human Adaptation to Agriculture https://academic.oup.com/mbe/article/35/12/2957/5112969?login=false

[8] Rise in Agriculture, Dietary Changes, May Be Linked to Adaptations ... https://academic.oup.com/mbe/article/34/6/1547/3829702