SO WHY DARWIN AND MENDEL?

By Darwin’s day, many scientists and philosophers had already begun to imagine that organisms, and perhaps the world as a whole, evolve.* Geology had opened up the layers of the earth below for study, taxonomy got biologists thinking about the similarities between different species, philosophers were questioning Judeo-Christian accounts of Creation, and paleontology and archaeology were bringing ancient bones to the light of day.

Charles Darwin and Gregor Mendel may not have been pioneers of imagination, but they had a great edge over some of their predecessors: scientific method. Darwin did not invent the idea of evolution, and Mendel did not invent the idea of heritability, but they are the fathers of their fields because they transformed these ideas into sound scientific hypotheses and gathered observable evidence to support them. The bread and butter of science (and maybe this is just my opinion) is the pursuit of predictable outcomes. Both Darwin and Mendel were able to create models where observable circumstances led to predictable outcomes.

• A hen is only an egg’s way of making another egg.
• All progress is based upon a universal innate desire on the part of every organism to live beyond its income.
• Man is God’s highest present development. He is the latest thing in God.
• Man is the only animal that can remain on friendly terms with the victims he intends to eat until he eats them.
• Man is the only animal that laughs and has a state legislature.

All above quotes are copied from http://www.brainyquote.com/quotes/authors/s/samuel_butler.html.

Little did I know, however, that one of Darwin’s predecessors in evolutionary thought was Darwin– Erasmus Darwin– his grandfather.

ABOUT ERASMUS

Erasmus Darwin’s interests were varied. He was not only a naturalist but also a poet, an inventor, a philosopher, a doctor, and a social advocate (he was a proponent of formal education for girls).

Quoting Wikipedia: “In notes dating to 1779, Darwin made a sketch of a simple liquid-fuel rocket engine, with hydrogen and oxygen tanks connected by plumbing and pumps to an elongated combustion chamber and expansion nozzle, a concept not to be seen again until one century later.”†

WORK IN NATURAL SCIENCE

Erasmus Darwin, as it turns out, did some very important writing. In the 1770′s and 1780′s, he led translations of “father of modern taxonomy” Carl Linnaeus’s botanical writings. In A System of Vegetables and The Families of Plants, he was the first to translate the Latin names of many plant species, as laid out by Linnaeus, into English.

In Zöonomia (1794-1796), Erasmus Darwin eloquently presented his theories on what would later be called evolution.

“The late Mr. David Hume, in his posthumous works, places the powers of generation much above those of our boasted reason; and adds, that reason can only make a machine, as a clock or a ship, but the power of generation makes the maker of the machine; and probably from having observed, that the greatest part of the earth had been formed out of organic recrements; as the immense beds of limestone, chalk, marble, from the shells of fish; and the extensive provinces of clay, sandstone, ironstone, coals from decomposed vegetables; all of which have been first produced by generation, or by the secretions of organic life; he concludes, that the world itself might have been generated, rather than created; that is, it might have been gradually produced from very small beginnings, increasing by the activity of its inherent principles, rather than by a sudden of evolution of the whole by the Almighty fiat.” *

… … …

“Would it be too bold to imagine that, in the great length of time since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind would it be too bold to imagine that all warm-blooded animals have arisen from one living filament, which the great First Cause endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions and associations, and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down these improvements by generation to its posterity, world without end!”†

THE EVOLUTION OF EVOLUTION

The quoted passages above have to be appreciated in their historical context. Lamarck did not write his famous works on the reproduction of novel traits until the early 19th century.  Gregor Mendel, often called the “father of genetics,” was only born in 1822. And Charles Darwin’s Origin of Species was not published until 1859. Even in the 1770′s, Erasmus Darwin was not the first to think about the concepts that now comprise our modern theory of evolution. In the first passage above, he cites philosopher David Hume. When we conflate evolution and (Charles) Darwinian evolution, we forget about all the perspectives and innovative ideas that shaped the discourse before and after Charles Darwin’s influential work. That is not to say he does not deserve a great deal of credit for articulating and popularizing evolutionary theory. It is important to keep in mind, though, that there were people who believed the world to be round before Columbus lived, that Columbus preceded Galileo, and that every great innovator has great-grandparents.

SOURCES AND FURTHER READING

* http://www.victorianweb.org/science/edarwin.html

† http://en.wikipedia.org/wiki/Erasmus_Darwin

http://www.strangescience.net/erasmus.htm

http://en.wikipedia.org/wiki/Carolus_Linnaeus

http://en.wikipedia.org/wiki/Jean-Baptiste_Lamarck

OR LACK THEREOF?

When I start to talk to someone new about evolution, I often get myself into an unfortunate argument–not intentionally, of course. Many perfectly intelligent people believe that as a species, human beings are no longer evolving. Immediately, to me, this notion is preposterous. And besides that, it is a sad illustration of how misunderstood, perhaps badly taught, are the key concepts of evolutionary theory.

Allow me to direct the reader to some definitions of evolution from the web. (Thank you, Google’s “define:” feature!)

EVOLUTION

• development: a process in which something passes by degrees to a different stage (especially a more advanced or mature stage); “the development of …
• (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms
  wordnet.princeton.edu/perl/webwn

• In biology, evolution is the process of change in the inherited traits of a population of organisms from one generation to the next. The genes that are passed on to an organism’s offspring produce the inherited traits that are the basis of evolution. en.wikipedia.org/wiki/Theory_of_evolution

Then there is the academic definition I learned in my genetics classes.

• Evolution can be defined as the change in allele frequencies in a population. faculty.virginia.edu/evolutionlabs/

EVOLUTION IN MODERN CONTEXT

Hopefully it is apparent now that evolution is not simply survival of the fittest, even if that is a very large part of it. Evolution is a constant process. Every population, species, genus, family, and so on, is evolving as I write this. Only extinct groups don’t evolve. Even if we cure all diseases, the process of evolution will continue in our species. You can think of alleles as little genetic differences between individuals or groups of individuals. Some allele differences are readily observable, such as eye color, and some are not. When a baby is born, it contains some of its mother’s and some of its father’s genetic information, thus changing the frequency of alleles in its population. Instantly. This is a very simple illustration, and may not seem very useful in studying evolutionary change over time, but it is the unceasing births and deaths within a population that allow evolution to continue. Heritable mutations in turn add to genetic diversity.

So what is the significance of these miniscule changes in allele frequency? Remember that selection can be positive, negative, or neutral. When a completely healthy person dies without having had a child, his or her genes have been selected against. Likewise when a person with a genetic disposition toward heart disease has a child, his or her genes have been selected for. In our modern society, evolution appears to have stagnated because selection is generally neutralized by medicine and good nutrition. Genetically “fit” individuals do not always pass on their genes because they have access to birth control and do not need extra hands in the field to keep the family fed, or to take care of them in their old age. Genetically “unfit” individuals can pass on their genes because of treatments, cures, and suppression therapies.

Consider in addition the sheer size of our population and how open and fluid it is, allowing foreign genes in and sending native genes out, and you should understand why large-scale evolutionary changes aren’t occuring here. There is simply no overwhelming push one way or another.

EVOLUTION YOU CAN SEE

Hundreds of years ago, people lived shorter lives, and generally didn’t grow as tall as we do today. Whether that is proof of genetic change, or just of better medicine and improved diet, is up for debate. Evidence of large-scale evolutionary change in modern humans since history began is scant to invisible. But evolution is not all about large-scale change. In humans, the process is probably just too slow to observe.

In my mind, there are three major reasons why evolutionary change can happen quickly or very gradually within a population:

1. Population size. In order for change to sweep over the population quickly, it needs to be very small.

2. K or r selected. In a species where offspring are plentiful and reproduce soon after birth (r-selected, i.e. rats), generation times are short, and change can happen rapidly. In a species where individuals invest in small numbers of long-lived offspring (K-selected, i.e. humans), generation times are long, and change happens slowly.

3. Environmental pressure. This is where human evolution is somewhat unique.

SOCIAL VS. BIOLOGICAL EVOLUTION

There is a prevailing idea that humans now evolve socially, rather than biologically. Hopefully at this point in my article I no longer need to argue on the latter clause; we are still evolving biologically. But the former needs addressing. As a species, we use our brains (themselves a product of evolution that began longer ago than we can fathom) to solve problems. Innovations and improvements are passed from generation to generation along with genetic data. The result is that when environmental pressures become intense, a biological coping mechanism is not always necessary.

Social evolution is not constrained in the same ways that biological evolution is, and so it can occur faster and thus more noticeably. With television, radio, and the Internet, an innovation from one corner of the globe can reach billions of people at an unprecedented speed. However, humans are not the only animals that can evolve socially. Other apes are capable of innovation and teaching, as are elephants, dolphins, and who knows what else. Social evolution can reduce the significance of biological evolution, but it cannot cause it to cease.

Mammals facing extinction threat –BBC News

PHOTOS: Parachute Spider, New Shrew on 2008 ”Red List” –National Geographic

Extinction Crisis Worsens; “Dow Jones” Approach Touted –National Geographic

THE IUCN

The International Union for Conservation of Nature, or the IUCN, was founded in 1948 and today comprises over 1,000 member organizations in 140 countries, according to its website. The IUCN’s Red List of Threatened Species, begun in 1963, is a comprehensive list of the conservation statuses of the world’s wildlife. Species and subspecies of concern are placed in the following categories:

• Least concern
• Near threatened
• Vulnerable
• Endangered
• Critically endangered
• Extinct in the wild
• Possibly extinct

The status of each species is monitored and evaluated by a Species Survival Commission (SSC) Specialist Group. Some Specialist Groups focus on specific species or families, while others are responsible for larger numbers of related species or even geographic or disciplinary areas .

IUCN.org offers a convenient directory to all its SSC Specialty Groups, which you can check out here.

If you’re in the mood for cute, take a thorough look at the Otter Specialist Group at http://www.otterspecialistgroup.org.

MEET THE PANGOLIN

©http://letopis.kulichki.net/2001/image2001/pangolin.jpg

The seven species of the single pangolin family Manis have their very own order, Pholidota. The name pangolin is Malaysian and refers to the animal’s habit of rolling itself into a ball when threatened.*

CONVERGENT EVOLUTION

Pangolins are certainly unique, but they share some behavioral and morphological traits with more familiar mammals. Sometimes called scaly anteaters, all pangolins eat burrowing insects like termites and ants, and lack teeth. Their scales are made of the same material as fur or hair, like those of armadillos. Once they were grouped in the order Edantata (which means “toothless”) with anteaters and armadillos, but they are no longer considered to be related species. Some current phylogenies place Pholidota in a clade (a discrete group of species related by evolution) with Carnivora, making carnivores such as dogs, cats, bears, mongooses, and weasels the pangolin’s closest living relatives.

SOURCES

http://www.ucmp.berkeley.edu/mammal/eutheria/pholidota.htm

*http://www.americazoo.com/goto/index/mammals/129.htm

http://en.wikipedia.org/wiki/Pangolin

http://www.bbc.co.uk/nature/wildfacts/factfiles/621.shtml

Mudskippers at the NY Aquarium. Photos by me.

THE AMBLING FISH

The most immediately unique trait of the mudskipper is that it can walk on land. Far from quadrupedal, it drags itself along like a true seal with powerful, modified front fins. Flexing and jumping, mudskippers can move quite quickly on land when they need to.

Mudskippers can also climb the mangroves and things that grow in their swampy habitats. The adorable, tiny, so-called “Indian” mudskippers (Periophthalmus sp.) housed at the New York Aquarium can be seen clinging to their fake mangroves as well as to the walls of their tank. A mudskipper’s ability to climb and stick to surfaces is due to its muscular pectoral fins and also to a suction disk located on its underside below its head.

Mudskippers are so well adapted to their amphibious lifestyle that some can spend up to 90% of their lives out of the water!

BURROWING BEHAVIOR

Like many species that live in tidal zones, the mudskipper’s daily routine is governed by a predictable tide. While the tide is low, despite the threat of predation from seabirds and terrestrial animals, mudskippers forage along the mudflats for small crustaceans and fishes. When the tide is high, however, they stay hidden from predatory fish inside deep burrows they’ve dug in the mud. Mudskippers have evolved an ingenious way of keeping their burrows oxygenated while completely submerged, sometimes for several hours. They literally gulp air from the surface, and then carry it down into a specially crafted chamber where the air is released, forming a bubble at the top of the chamber. Research suggests that mudskippers use this same behavior to keep their eggs oxygenated in nursery chambers.

The burrow is a mudskipper’s refuge and a highly defended marker of his territory. Mudskipper species can be highly territorial. The Indian mudskippers at the New York Aquarium are not nearly as territorial as other species, and can be kept in close quarters together. Occasionally an individual will show territorial aggression, however, by lifting its brightly colored dorsal fin as a warning to a nearby individual.

During breeding season, males of some species show off their decorated burrows and do elaborate dances and flips to attract females. Little is known about mudskipper breeding, however.

CLASSIFICATION AND TAXONOMY

CLASS: Actinopterygii (ray-finned fishes)

ORDER: Perciformes (perch-like fishes; the largest order of vertebrates!)

FAMILY: Gobiidae (gobies)

SUBFAMILY: Oxudercinae (mudskippers)

MANGROVE HABITAT CONSERVATION

Mudskippers around the world are threatened by habitat loss. Mangrove swamps not only provide valuable habitat for a variety of fascinating animals, but they also serve as natural buffers to erosion, storm surges and tsunamis, and also trap pollutants. Coastal human populations around the world benefit from strong mangrove ecosystems, and the loss of these ecosystems is tangibly affecting many regions.

SOURCES AND ADDITIONAL READING

http://en.wikipedia.org/wiki/Mangrove

http://species.wikimedia.org/wiki/Oxudercinae

http://www.naturalhistorymag.com/0902/0902_feature.html

http://newyorktails.com/mudskippers.htm

http://newyorkaquarium.org

You can also see mudskippers (Periophthalmus barbarus) at the Bronx Zoo!

Its most striking feature was that it had white bands on its wings and tail that seemed to run lengthwise rather than widthwise, making it appear elegant and streamlined. Thanks to Google and WhatBird.com, I was able to identify it beyond a doubt as a northern mockingbird.

photo by flyingtyrtle: http://flyingturtle.blogspot.com

These birds eat fruit and insects. WhatBird.com provides this map of their range.

CLASSIFICATION

CLASS: Aves (Birds)

ORDER: Passeriformes (More than half of all birds are passerines, or perching birds.*)

FAMILY: Mimidae (Mockingbirds and thrashers)

GENUS: Mimus (Mockingbirds)

SCIENTIFIC NAME: Mimus polyglottos

STATE BIRD

The northern mockingbird is not the state bird of New York, of course. But it is the state bird of five U.S. states: Tennessee, Arkansas, Texas, Florida, and Mississippi.

SOURCES AND ADDITIONAL LEARNING

*http://en.wikipedia.org/wiki/Passerine

http://identify.whatbird.com/obj/158/_/Northern_Mockingbird.aspx

http://en.wikipedia.org/wiki/List_of_U.S._state_bird

(If you are flyingtyrtle and object to my using your photo, please let me know and I will remove it.)

LOVE

Domesticated rats make excellent pets. They are loyal, affectionate, intelligent, and have a range of personalities. They’re more like puppies than they are like hamsters. They can be trained to respond to their own names, to perform “tricks,” or even to use a litter box inside their cage. My rats can’t do any of those things, but that is due to my lack of patience, not their lack of intelligence. They do seem to know when I’m talking about them individually, and they respond to my kissy noises and attempts to get their attention. They naturally poop and pee in their cage and hold it in when they’re outside the cage, unless they’re kept out too long. They do mark their territory, both the boy and the girl, but they can’t help that.

Milo, a black hooded, is a former laboratory rat from Hunter College in New York City, my alma mater. Ginger, a cinnamon, came home with me months later from the pet store where I work, and was promptly spayed. If you’re wondering what it might cost to spay a rat in Brooklyn, it cost me $205. Worth every penny. She healed very quickly and not only is she spared the unnecessary trauma of ratty childbirth, but she is less likely to develop cancerous tumors in her later life.

Before I bought Ginger, I tried introducing Milo to a pair of little boy rats. Being an intact male who had grown up isolated from other rats, Milo was adamantly against bonding with them. It is not only possible, but common to successfully introduce male rats. It is easier to introduce neutered males than intact males. Sometimes, however, a rat is just not interested. And Milo was not interested. The whole time their cages were next to one another, Milo was puffed up, irritated, and hostile toward the babies. He would stare them down, hissing and breathing heavily, for 15 minutes or so at a time. After three failed attempts at introductions, I gave up, and I found the baby boys a good home with another rat lover.

In the first three and a half weeks or so that I worked at the pet store, Ginger and I bonded. When I found out we were sending our female rats to other stores due to low sales, I could not say goodbye to her. The other rats in the store were all PEW’s, or pink-eyed whites, the standard feeder variety that creep a lot of people out. How Ginger, a fancy rat, got mixed in there I still don’t know. But I fell in love with her personality.

SCIENCE

Rats are rodents. Rodents are mammals. I have heard customers say that rats, mice, or hamsters are invertebrates, or even that they have no bones, but it should be obvious that this is untrue. All mammals are chordates, as are birds, reptiles, amphibians, and fishes. The order rodentia is distinguished by upper and lower incisors that grow continuously. All rodents share the need to gnaw on hard materials to keep their teeth from growing too long. Most of the small animals you find at the pet store are rodents, excluding rabbits (order: lagomorpha) and ferrets (order: carnivora).

The most fascinating part of rat anatomy is the tail. The tail is used for thermoregulation (allowing heat to escape) as well as for balance (watch a rat walk the tightrope on the narrowest surface, and you’ll understand).

image source: http://www.ratbehavior.org

The tail scares people, but it’s just a hairless extension of the spine!

SOURCES AND ADDITIONAL LEARNING

http://www.ratbehavior.org/

http://en.wikipedia.org/wiki/Rodent