Module 12 Blog Post

Diseases of Civilization: Acne 

Acne is one of the most common diseases of civilization, occurring in most populations around the world. It may not be as deadly as others like cancer and heart disease but it can signal an unhealthy diet or illness. How it occurs: Acne forms when a hair follicle is clogged by dead skin cells and sebum. Bacteria may be trapped in the follicle too, producing puss and causing inflammation. You usually see the worst acne in teenagers, when they are going through puberty.

 Acne Vulgaris: A Disease of Western Civilization | Acne | JAMA Dermatology | JAMA Network

This article presents interesting data concerning the absence of acne in the Kitavan islanders, and Ache hunter gatherers in Paraguay, as well as anecdotal evidence from medical professionals that acne was absent in Inuit and islander populations. These populations eat mostly natural foods like meats, fruits, vegetables; which are also all low glycemic index foods. There's not a lot of dairy, grains, sugar, or oils in their diets according to this source. Interestingly though, the article mentions that 3/4 Kitavans are smokers. The Ache people were similar, a population of hunter gatherers that were contacted and introduced to western good like bread, sugar, and tea in the 1970s. Following the introduction of western diet, diseases associated with it did not become more common.

Is Acne Fed by the Western Diet? (webmd.com)

This resource is good if you want to read about how the western diet influences the hormones and metabolic processes in the body. More specifically, the high glycemic index foods that are in the western diet can increase levels of insulin and IGF-1. The increase of these hormones leads to more sebum being produced. A really interesting fact from this article states that teens are more susceptible to acne because when you're still growing insulin resistance is a natural part of tissue growth. The article talks about the Academy of Dermatology not being able to say that "food causes acne", mostly because of papers written in the late 1900s, like one paper that specifically tested whether or not chocolate was a cause (the experiment showed that it didn't cause acne)

Dairy and Acne: How They’re Connected, The Myth and the Science (dermcollective.com)

This source has links to quite a few different studies that support the claim that milk itself may not be to blame for acne. Yogurt and cheese don't have any conclusive studies yet. Skim milk is shown to cause more acne, probably due to added sugars and whey protein. Milk also has naturally occurring hormones which can affect IGF-1. Fermented dairy, according to this source, was also shown to be correlated with decreasing acne.

There's quite a bit of evidence that shows that the western diet mainly causes/exacerbates acne due to sugar and hormones.

Sources

Is Acne Fed by the Western Diet? (webmd.com)

Acne Vulgaris: A Disease of Western Civilization | Acne | JAMA Dermatology | JAMA Network

Dairy and Acne: How They’re Connected, The Myth and the Science (dermcollective.com)

The age-old problem of acne - ScienceDirect This article is pretty interesting, it just kind of goes through how acne was described in history

Module 11 Blog Post: Speciation

Speciation in Nature

Hybridization takes two species that are evolved to be adapted to a specific environment. If two species from different environments interbreed, this could cause those mixed offspring to be less adapted to both environments, and the fitness of the hybrid will be lower than the fitness of their parents.A lot of zoo animal type hybrids, who may never mate in the wild, give birth to offspring that have multiple medical issues, live shorter lives, or are not able to reproduce.The only example of successful hybridization a marine mammal is the clymene dolphin (maybe, there was conflicting evidence online). The sources I looked through said it was possibly a hybrid of the spinner dolphin and the striped dolphin, both of which have habitats that allow for them to interact with one another. Examples of mammals in nature were hard to find because it can be hard to tell whether or not an animal is a hybrid or not (cryptic species, hard to test). There are also records of bottlenose dolphin/ false killer whale hybrids that exist in nature and also a viable hybrid that lives in captivity; the hybrid had two offspring that both passed. The resource listed below concerning the study of clymene dolphin hybrids claims that the genetic diversity created by hybridization can be beneficial. It can introduce genetic variation and create new species to fill new ecological niches. There are more species of dolphins, whales, and porpoises breeding and having viable offspring but its not common. For the hybridization to be beneficial and create viable offspring, maybe its just somewhat up to chance and the separate evolutionary paths each species takes and the types of selection acting upon both.

Whale-Dolphin Hybrids - Cross Species Hybridization (google.com)

Sources

Wholphin / Wolphin - WHALE FACTS

Don't call it a wholphin: first sighting of rare whale-dolphin hybrid | Whales | The Guardian

Hybrid Speciation in a Marine Mammal: The Clymene Dolphin (Stenella clymene) (nih.gov)

Module 10: Sexual Dimorphism

Pipefish Courtship

Sexual dimorphism evolves for a few reasons but the main cause of these differences in males and females is due to the fact that each sex has a different roll when it comes to how they experience selection. Males can develop characteristics like horns, larger size, ornamental feathers...etc. due to competition with other males and the need to impress females and pass on their genes. Some of these characteristics/ competitions allow the animal to compete with others and in some cases, the ones with the best fitness will pass on their genes.

Pregnancy is very costly for females of any species. Extra sustenance and is required due to the energetic costs of it. However, pipefish roles are reversed and the males gestate the offspring until birth. In pipefish, seahorses, and sea dragons, the females pass the eggs on to the males in a pouch or on their tails. Then the males fertilize the eggs in the designated pouch or tail, where they are kept until they hatch. Carrying offspring is a very costly and takes a lot of extra resources and stress on the body but the females of these fish only have to expend the energy it takes to make the eggs, which would usually be the males role. Instead the males take on the physiologically taxing role of carrying the offspring. Sexually dimorphic characteristics like the pipefish sail, antlers, and intricate peacock feathers are costly too so the roles in pipefish are generally reversed; the females court and the males carry young. Female courtship probably evolved in pipefish due to this reason. The males are able to choose a mate who they think will produce good offspring that are worth the cost to carry.

Similar to pipefish, male seahorses and sea dragons also carry offspring; but unlike pipefish, they have generally common sex roles in mating and courting. The males generally compete for female choice. Mating rituals involve mirror dancing and tail grabbing in seahorses. They are sexually dimorphic in some ways, like body and tail length, but they don't have flashy costly displays like the female pipefish. Maybe pipefish sail is a good indicator of health and that is how the female specific characteristic evolved. It also probably helps male pipefish make what they see as the best choice, to help choose the fittest female and have the fittest offspring.

Sources

BBC - Earth News - Ghostly 'dance of a sea dragon' - this short article explains the dancing courtship ritual of sea dragons and seahorses