Does anyone know of an article or something explaining why animal products are the foundation of so many diets/meals despite there being over 20,000 edible plants in the world? If there's tens of thousands of choices, isn't it strange that humans continue to build all their meals around the same 4 or 5 foods?
It's an extensive answer, but I'll try to make a cliff notes version as much as I'm aware.
The genesis of the issue can be somewhat drawn to when protein was first discovered in the mid 1800s. Animal protein was then found to be the most complete protein in comparison to plant protein. You can even find traces of it in the medical literature today as "high quality" protein refers to animal protein, a relic of when it was first discovered to be a complete protein.
At the time, in western countries animal protein consumption was seen as a sign of "advanced" civilization and the thinking has persisted to this day. Eating mostly or all plants was viewed as something "sub" humans did (IE farming rural populations/tribes disconnected from advanced civilization), not something civilized and cultured people do.
In spite of the growing evidence that animal protein consumption is not good for humans, we continue to do so and that evidence is ignored and/or repressed. It isn't a back room cabal or secret handshake agreements, it's just powerful interests are invested in the perpetuation of animal product consumption.
Here in the US, we subsidize these industries in the billions via grain and antibiotic purchases (roughly 80% of antibiotics purchased in the US are purchased by animal/agri business), and they rake in billions a year, so clearly agriculture/dairy/cattleman's associations have no interest in seeing reductions in meat consumption. These institutions spend billions on representatives to ensure government doesn't get too involved in public wide dietary health concerns. You'll see generic recommendations for "lowering your saturated fat consumption (vast majority of saturated fat is only found in animal foods, hint hint)" but when you start naming specific food, industry will use all their political might and lobbyist to ensure the government doesn't name name's in it's recommendations.
There was even a strong push by the World Health Organization to put a "traffic light" system onto food labels to help guide consumers on European food labels. Studies were promising that such a labeling system would be very effective at educating the public on what foods they should and shouldn't avoid. US food interests kicked in to gear putting pressure on their government representatives for the US to pull all funding from WHO if the traffic light system were to be implemented. Ultimately US food interests won out and the WHO backed down from the labeling system. A WHO representative said it was the most aggressive campaign they had ever seen (even more than what tobacco had previously done).
Even some of the institutions you would assume might have our best health interests in mind don't here in the US. Some of the Academy of Nutrition and Dietetics Association's biggest sponsor's are the Cattleman's Association, Confectioners Association, the Egg Nutrition Center, Mead-Johnson (they specialize in infant formula), and even a few pharmaceutical companies. Clearly a who's who of looking out for individual's health and well being.
Even an organization such as the American Cancer Society is not immune. Ironically, they were founded by a statistician, Frederick Hoffman, who had found a correlation, even back in the early 1900s, between increased animal consumption and increased cancer rates. You'll find little mention of him because he wasn't a physician (and he didn't espouse the "higher minded" cancer treatments as vigorously as most founding members would have hoped). But many of the original board members were either surgeons, radiologists and oncologists. Not a single dietician...and what are the most common forms of cancer treatment that persist even to this day? Surgery, radiology and chemotherapy, it's not a coincidence. It became an "in-crowd" back then that has persisted to this day in most leading cancer institutions.
Side note: to this day, you'll never find any population studies that show an increase in animal products leads to a decrease (or even neutral) cancer or mortality rates.
So no political, commercial or institutional will to stop animal consumption. Makes it tough before you take into account the individual will is weak in most folks too. Even a relatively progressive place like this (ERA), has barely any will to fight against it, since most are indoctrinated by industry. Food is an addiction and diet has become religion. We are literally killing ourselves by burning up the planet (in large part due to our diets) and switching to a fully plant based diet on a global scale would lead to incredible gains in the fight against climate change but people (even on ERA) lose their minds when you tell them to eat less meat....that's not even accounting for the responses to suggesting to stop meat consumption completely. There is a line by Dr. Milton Mills where he says something to the effect of you've never seen addiction until you've taken a chicken leg out of someone's hand - sounds about right to me.
Look at any weight loss thread and I can't help but just shake my head at all the keto diet recommendations. It's a terrible diet that has no long term studies showing positive results and really requires it's own long post to get into the details, but safe to say, it's not good for us or the planet (since most keto diets are recommending the consumption of a heavy amount of animal fat and protein). And I feel bad for those folks as the studies that are out there based on what keto diets consist of imply those who eat keto diets are increasing their likely hood of cardiovascular diseases, like strokes and heart attacks, cancer, dementia along with lower quality of life associated with ED, lower back pain, pain in other joints, angina, among a myriad of other issues. My favorite are those weight loss threads where the OP says "help me lose weight ERA - but I'm not giving up meat and dairy." The CI-CO folks and keto proponents love to hear that though, too bad people are far too interested in anecdotes as opposed to analysis (a fact that many snake oil weight loss advertisers are well aware of).