Notable speakers at the event included the human rights campaigner Peter Tatchell and author Richard Dawkins. Victims of child abuse by Catholic priests also spoke to the crowd.
The event passed off without incident and attracted five times the number of people originally expected.
That's not how it works.
Evolution is about adaptation over time to develop new features. It was all one species, but as population grew, they migrated to different climates, elevations, ext., and adapted properly to become more suitable for the environment.
And by the way, we're apes.
No offense but you sounded really stupid mixing those up ._.
Wrong evolution means at one point... Species A + Species A = Species B... Hence Humans coming from Monkeys... Otherwise why else would you associate that with Evolution...? We're constantly told that Evolution means Humans come from Monkeys, yet every time we ask how, we're told Evolution doesn't work that way...
If what you said is true... Why are wolves still here? Shouldn't the Earth be too hectic for them? Hence the existence of the other Canine breeds?
Hence... Dogs... Cats... And Horses...
So I will ask again... Name two entirely different species of Primates that are capable of mating with each other...
Felines... Lions and Tigers... Lepoards and Jaguars or Panthers... Therefore Cats come from the same place...
Canines... As long as the Size matches up... A dog can probably mate with a fox... Seeing as how all dogs apparently come from Wolves and we all know about the Wolf Huskies... Hence Dogs come from the same place...
Equines... A Donkey and a Horse... A Zebra and A Horse... Thus 2 + 2 = 4 and a Donkey and a Zebra... Hence Equines come from the same place...
Now either you can block me... Out of my sheer ignorance out of your bullshit theories that you just LOVE changing with every new contradiction you assholes come across... Or you can name me 2 different Species of Primates that are Capable of Mating with each other...
Thus proving why 2 Species A's can make a Species B but Species B canNOT mate backwards with Species A... IF it was in fact Species A that made Species B in the first place...
Otherwise... Scientists are complete morons for Relating Humans to any Monkey or Ape JUST because out of Sheer Coincidence... All 3 things HAPPEN to have hands that look the same... What you call evolution... I call Coincidence...
And fuck a 2% chromosome difference... Humans are able to survive with pig parts implanted in them... Doesn't mean we're related to pigs... When has a human EVER been able to survive with a Monkey or Ape transplant?
How can we come from them if none of our parts match when needed? Huh? Or are you going to give me that bullshit answer that explains how A Rhino is related to a Horse?...
The basic theory of evolution is surprisingly simple. It has three essential parts:
- It is possible for the DNA of an organism to occasionally change, or mutate. A mutation changes the DNA of an organism in a way that affects its offspring, either immediately or several generations down the line.
- The change brought about by a mutation is either beneficial, harmful or neutral. If the change is harmful, then it is unlikely that the offspring will survive to reproduce, so the mutation dies out and goes nowhere. If the change is beneficial, then it is likely that the offspring will do better than other offspring and so will reproduce more. Through reproduction, the beneficial mutation spreads. The process of culling bad mutations and spreading good mutations is called natural selection.
- As mutations occur and spread over long periods of time, they cause new species to form. Over the course of many millions of years, the processes of mutation and natural selection have created every species of life that we see in the world today, from the simplest bacteria to humans and everything in between.
Billions of years ago, according to the theory of evolution, chemicals randomly organized themselves into a self-replicating molecule. This spark of life was the seed of every living thing we see today (as well as those we no longer see, like dinosaurs). That simplest life form, through the processes of mutation and natural selection, has been shaped into every living species on the planet.
Can such a simple theory explain all of life as we know it today? Let's start by understanding how life works and then look at some examples.
Evolution can be seen in its purest form in the daily evolution ofbacteria. If you have read How Cells Work, then you are familiar with the inner workings of the E. coli bacteria and can skip this section. Here's a quick summary to highlight the most important points in How Cells Work:
- A bacterium is a small, single-celled organism. In the case of E. coli, the bacteria are about one-hundredth the size of a typical human cell. You can think of the bacteria as a cell wall (think of the cell wall as a tiny plastic bag) filled with various proteins, enzymes and other molecules, plus a long strand of DNA, allfloating in water.
- The DNA strand in E. coli contains about 4 million base pairs, and these base pairs are organized into about 1,000 genes. A gene is simply a template for a protein, and often these proteins are enzymes.
- An enzyme is a protein thatspeeds up a particular chemical reaction. For example, one of the 1,000 enzymes in an E. coli's DNA might know how to break a maltose molecule (a simple sugar) into its two glucose molecules. That is all that that particular enzyme can do, but that action is important when an E. coli is eating maltose. Once the maltose is broken into glucose, other enzymes act on the glucose molecules to turn them into energy for the cell to use.
- To make an enzyme that it needs, the chemical mechanisms inside an E. coli cell make a copy of a gene from the DNA strand and use this template to form the enzyme. The E. coli might have thousands of copies of some enzymes floating around inside it, and only a few copies of others. The collection of 1,000 or so different types of enzymes floating in the cell makes all of the cell's chemistry possible. This chemistry makes the cell "alive" -- it allows the E. coli to sense food, move around, eat and reproduce. See How Cells Work for more details.
You can see that, in any living cell, DNA helps create enzymes, and enzymes create the chemical reactions that are "life."
The process of evolution acts on an E. coli cell by creating a mutation in the DNA. It is not uncommon for the DNA strand in an E. coli bacterium to get corrupted. An X-ray, a cosmic ray or a stray chemical reaction can change or damage the DNA strand. In most cases, a particular E. coli cell with mutated DNA will either die, fix the damage in the strand or fail to reproduce. In other words, most mutations go nowhere. But every so often, a mutation will actually survive and the cell will reproduce.
Imagine, for example, a bunch of identical E. coli cells that are living in a petri dish. With plenty of food and the right temperature, they can double every 20 minutes. That is, each E. coli cell can duplicate its DNA strand and split into two new cells in 20 minutes.
Now, imagine that someone pours an antibiotic into the petri dish. Many antibiotics kill bacteria by gumming up one of the enzymes that the bacteria needs to live. For example, one common antibiotic gums up the enzyme process that builds the cell wall. Without the ability to add to the cell wall, the bacteria cannot reproduce, and eventually they die.
When the antibiotic enters the dish, all of the bacteria should die. But imagine that, among the many millions of bacteria living in the dish, one of them acquires a mutation that makes its cell-wall-building enzyme different from the norm. Because of the difference, the antibiotic molecule does not attach properly to the enzyme, and therefore does not affect it. That one E. coli cell will survive, and since all of its neighbors are dead, it can reproduce and take over the petri dish. There is now a strain of E. coli that is immune to that particular antibiotic.
In this example, you can see evolution at work. A random DNA mutation created an E. coli cell that is unique. The cell is unaffected by the antibiotic that kills all of its neighbors. This unique cell, in the environment of that petri dish, is able to survive.
E. coli are about as simple as living organisms can get, and because they reproduce so rapidly you can actually see evolution's effects on a normal time scale. In the past several decades, many different types of bacteria have become immune to antibiotics. In a similar way, insects become immune to insecticides because they breed so quickly. For example, DDT-resistant mosquitoes evolved from normal mosquitoes.
In most cases, evolution is a much slower process.
As explained in How Human Reproduction Works, higher organisms like plants, insects and animals reproduce sexually, and this process makes the actions of evolution more interesting. Sexual reproduction can create a tremendous amount of variation within a species. For example, if two parents have multiple children, all of the children can be remarkably different. Two brothers can have different hair color, different heights, different blood types and so on. Here's why that happens:
Photo courtesy U.S. DOE, Human Genome Project
- Instead of a long loop of DNA like a bacterium, cells of plants and animals have chromosomes that hold the DNA strands. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. Fruit flies have five pairs. Dogs have 39 pairs, and some plants have as many as 100.
- Chromosomes come in pairs. Each chromosome is a tightly packed strand of DNA. There are two strands of DNAjoined together at the centromere to form an X-shaped structure. One strand comes from the mother and one from thefather.
- Because there are two strands of DNA, it means that animals have two copies of every gene, rather than one copy as in an E. coli cell.
- When a female creates an egg or a male creates a sperm, the two strands of DNA must combine into asingle strand. The sperm and egg from the mother and father each contribute one copy of each chromosome. They meet to give the new child two copies of each gene.
- To form the single strand in the sperm or egg, one or the other copy of each gene is randomly chosen. One or the other gene from the pair of genes in each chromosome gets passed on to the child.
Because of the random nature of gene selection, each child gets a different mix of genes from the DNA of the mother and father. This is why children from the same parents can have so many differences.
A gene is nothing but a template for creating an enzyme. This means that, in any plant or animal, there are actually two templates for every enzyme. In some cases, the two templates are the same (homozygous), but in many cases the two templates are different (heterozygous).
Here is a well-known example from pea plants that helps understand how pairs of genes can interact. Peas can be tall or short. The difference comes, according to Carol Deppe in the book "Breed your own Vegetable Varieties":
...in the synthesis of a plant hormone called gibberellin. The "tall" version of the gene is normally the form that is found in the wild. The "short" version, in many cases, has a less active form of one of the enzymes involved in the synthesis of the hormone, so the plants are shorter. We refer to two genes as alleles of each other when they are inherited as alternatives to each other. In molecular terms, alleles are different forms of the same gene. There can be more than two alleles of a gene in a population of organisms. But any given organism has only two alleles at the most. Shorter plants usually cannot compete with the taller forms in the wild. A short mutant in a patch of tall plants would be shaded out. That problem isn't relevant when a human plants a patch or field with nothing but short plants. And short plants may be earlier than tall ones, or less subject to lodging (falling over) in the rain or wind. They also may have a higher proportion of grain to the rest of the plant. So shorter plants can be advantageous as cultivated crops. Specific mutations or alleles are not good or bad in and of themselves, but only within a certain context. An allele that promotes better growth in hot weather may promote inferior growth in cold weather, for example.
One thing to notice in Deppe's quote is that a mutation in a single gene may have no effect on an organism, or its offspring, or its offspring's offspring. For example, imagine an animal that has two identical copies of a gene in one allele. A mutation changes one of the two genes in a harmful way. Assume that a child receives this mutant gene from the father. The mother contributes a normal gene, so it may have no effect on the child (as in the case of the "short" pea gene). The mutant gene might persist through many generations and never be noticed until, at some point, both parents of a child contribute a copy of the mutant gene. At that point, taking the example from Deppe's quote, you might get a short pea plant because the plant does not form the normal amount of gibberellin.
Another thing to notice is that many different forms of a gene can be floating around in a species. The combination of all of the versions of all of the genes in a species is called the gene pool of the species. The gene pool increases when a mutation changes a gene and the mutation survives. The gene pool decreaseswhen a gene dies out.
One of the simplest examples of evolution can be witnessed in an E. coli cell. To get a better grip on the process, we'll take a look at what happens in this cell.
As mentioned in the previous section, many things can cause a DNA mutation, including:
- Cosmic Rays
- Nuclear Radiation
- Random chemical reactions in the cell
Therefore, mutations are fairly common.
According to "Molecular Biology of the Cell":
Only about one nucleotide pair in a thousand is randomly changed every 200,000 years. Even so, in a population of 10,000 individuals, every possible nucleotide substitution will have been "tried out" on about 50 occasions in the course of a million years, which is a short span of time in relation to the evolution of species. Much of the variation created in this way will be disadvantageous to the organism and will be selected against in the population. When a rare variant sequence is advantageous, however, it will be rapidly propagated by natural selection. Consequently, it can be expected that in any given species the functions of most genes will have been optimized by random point mutation and selection.
According to the book "Evolution," by Ruth Moore, it is possible to speed up mutations with radiation:
So Muller put hundreds of fruit flies in gelatin capsules and bombarded them with X-rays. The irradiated flies were then bred to untreated ones. In 10 days thousands of their offspring were buzzing around their banana-mash feed, and Muller was looking upon an unprecedented outburst of man-made mutations. There were flies with bulging eyes, flat eyes, purple, yellow and brown eyes. Some had curly bristles, some no bristles...
As you saw in the previous section, mutations are a random and constant process. As mutations occur, natural selection decides which mutations will live on and which ones will die out. If the mutation is harmful, the mutated organism has a much decreased chance of surviving and reproducing. If the mutation is beneficial, the mutated organism survives to reproduce, and the mutation gets passed on to its offspring. In this way, natural selection guides the evolutionary process to incorporate only the good mutations into the species, and expunge the bad mutations.
The book "Extinct Humans," by Ian Tattersall and Jeffrey Schwartz, puts it this way:
...in every generation, many more individuals are produced than ever survive to maturity and to reproduce themselves. Those that succeed -- the "fittest" -- carry heritable features that not only promote their own survival but are also passed along preferentially to their offspring. In this view, natural selection is no more than the sum of all those factors that act to promote the reproductive success of some individuals (and its lack in others). Add the dimension of time, and over the generations natural selection will act to change the complexion of each evolving lineage, as advantageous variations become common in the population at the expense of those less advantageous.
Let's look at an example of natural selection from How Whales Work.
The ancestors of whales lived on land -- there is evidence of the evolution of the whale from life on land to life in the sea (read How Whales Work for details), but how and why did this happen? The "why" is commonly attributed to the abundance of food in the sea. Basically, whales went where the food was. The "how" is a bit more perplexing: Whales are mammals, like humans are, and like humans, they lived and walked on solid ground, breathing air into their lungs. How did whales become sea creatures? One aspect of this evolution, according to Tom Harris, author of How Whales Work, is explained as follows:
To make this transition, whales had to overcome a number of obstacles. First of all, they had to contend with reduced access to breathable air. This led to a number of remarkable adaptations. The whale's "nose" moved from the face to the top of the head. This blowhole makes it easy for whales to breathe in air without fully surfacing. Instead, a whale swims near the surface, arches its body so its back briefly emerges and then flexes its tail, propelling it quickly to lower depths.
Odd as it seems that the whale's "nose" actually changed positions, the theory of evolution explains this phenomenon as a long process that occurs over perhaps millions of years:
- Random mutation resulted in at least one whale whose genetic information placed its "nose" farther back on its head.
- The whales with this mutation were more suited to the sea environment (where the food was) than "normal" whales, so they thrived and reproduced, passing on this genetic mutation to their offspring:Natural selection "chose" this trait as favorable.
- In successive generations, further mutations placed the nose farther back on the head because the whales with this mutation were more likely to reproduce and pass on their altered DNA. Eventually, the whale's nose reached the position we see today.
Natural selection selects those genetic mutations that make the organism most suited to its environment and therefore more likely to survive and reproduce. In this way, animals of the same species who end up in different environments can evolve in completely different ways.
Keep in mind that not all mutations are bad. Some are actually beneficial.
Imagine that you take a group of Saint Bernards and put them on one island, and on another island you put a group of Chihuahuas. Saint Bernards and Chihuahuas are both members of the species "dog" right now -- a Saint Bernard can mate with a Chihuahua (probably through artificial insemination) and create normal puppies. They will be odd-looking puppies, but normal puppies nonetheless.
Given enough time, it is possible to see how speciation -- the development of a new species through evolution -- could occur among the Saint Bernards and the Chihuahuas on their respective islands. What would happen is that the Saint Bernard gene pool would acquire random mutations shared by all of the Saint Bernards on the island (through interbreeding), and the Chihuahuas would acquire a completely different set of random mutations shared by all of the Chihuahuas on their island. These two gene pools would eventually become incompatible with one another, to the point where the two breeds could no longer interbreed. At that point, you have two distinct species.
Because of the huge size difference between a Saint Bernard and a Chihuahua, it would be possible to put both types of dogs on the same island and have the exact same process occur. The Saint Bernards would naturally breed with only the Saint Bernards and the Chihuahuas would naturally breed with only the Chihuahuas, so speciation would still occur.
If you put two groups of Chihuahuas on two separate islands, the process would also occur. The two groups of Chihuahuas would accumulate different collections of mutations in their gene pools and eventually become different species that could not interbreed.
The theory of evolution proposes that the process that might create a separate Chihuahua-type species and Saint Bernard-type species is the same process that has created all of the species we see today. When a species gets split into two (or more) distinct subsets, for example by a mountain range, an ocean or a size difference, the subsets pick up different mutations, create different gene pools and eventually form distinct species.
Is this truly how all of the different species we see today have formed? Most people agree that bacteria evolve in small ways (microevolution), but there is some controversy around the idea of speciation (macroevolution). Let's take a look at where the controversy comes from.
We will be a part of the big protest against the Pope in September.
I hope, it is okay for you