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Joy of Science
Experience the evolution of the
Universe, Earth and Life
•  Review of last class
•  Introduction
•  Contents of today’s lecture
•  Quiz time
Unless otherwise noted, all pictures are taken from wikipedia.org
Evolution of Life - Review n  Evidences for the fact of evolution
- Fossil record: Ex) the fossil record of horses, eye stalk changes of trilobite
- Biochemical evidence: genetic information by comparing sequences of amino acids
Ex) cytochrome C: all cells use in metabolism
- Vestigial organs: organs that have no use.
Ex) human - appendix, wisdom teeth, coccyx (tail bone)
n  Two stages of life’s evolution
1. Chemical evolution – this week
2. Natural selection: -Charles Darwin’s Origin of Species
-Particular genes that give advantages to match with the given
environment will more likely to be passed to the next generation
n  Geological time: there are several time boundaries in the Earth history
n  Mass extinctions and rate of evolution: sudden extinctions of large numbers of
species
Review 1
n  One of the universally possessed proteins that has been analyzed extensively
for biochemical evidence for evolution is
1. DNA
2. RNA
3. cytochrome C
4. enzymal RNA
5. amino acids
Review 1
n  One of the universally possessed proteins that has been analyzed extensively
for biochemical evidence for evolution is
1. DNA
2. RNA
3. cytochrome C
4. enzymal RNA
5. amino acids
Review 2
n  Which of the following represents a vestigial organ?
1. thumb
2. appendix
3. eye
4. stomach
5. elbow
Review 2
n  Which of the following represents a vestigial organ?
1. thumb
2. appendix
3. eye
4. stomach
5. elbow
Review 3
n  Dinosaurs disappeared approximately
1. 50 million years ago
2. 65 million years ago
3. 100 million years ago
4. 200 million years ago
5. 250 million years ago
Review 3
n  Dinosaurs disappeared approximately
1. 50 million years ago
2. 65 million years ago
3. 100 million years ago
4. 200 million years ago
5. 250 million years ago
Mystery of Life
Today’s Keywords
evolution, fossil, extinct, vestigial organ, chemical
evolution, natural selection, adaptation, mass extinction
Unanswered Questions…
n  The Origin of Life:
How could the first cell occur on Earth?
n  Can we communicate with extraterrestrial intelligent
life someday? Or, are human beings the only
intelligent life forms in the Universe?
Contents
n  Chemical evolution
n  The first cell
n  The evolution of human beings
Chemical Evolution
n  Chemical Evolution: - the first step in life’s long history
- the process by which rocks, water, and gases chemically
combined to become the first living cell
n  The question on the first creation of living cells hasn’t been clearly answered yet
n  Miller-Urey experiment: The first important experiment relating to chemical evolution
performed by Miller & Urey
- started with the assumption that Earth’s early atmosphere contained simple
compounds of principally of hydrogen (H), carbon (C), oxygen (O), and nitrogen (N)
- mixed simple compounds including water vapor (H2O), methane (CH4), hydrogen (H2),
and ammonia (NH3) in as flask
- added electric sparks to the mixed gases in order to make the experimental
environment as that of the early Earth with powerful lighting
àThe result: the liquid in the flask became cloudy and dark brown color
èAnalysis of the brownish liquid: a large number of amino acids, carbohydrates, and
other basic building blocks of life!!!
Miller-Urey Experiment
Chemical Evolution
n  Primordial Soup hypothesis
* M-U experiment and subsequent experiments had shown that natural process in the
oceans of the early Earth might generate the modules of life’s important molecules
* All sorts of organic molecules, including lipids and bases, as well as
long protein chains and nucleic acid can be made using more simple chemical
molecules such as nitrogen (N2) and carbon dioxide (CO2) than methane or ammonia
à Early Earth’s oceans produced a rich broth of amino acids and other molecules
created by M-U process for perhaps several hundred million years: Primordial Soup
* The conditions of early Earth’s oceans
- The oceans in primitive Earth had all primary chemical ingredients
- Additional molecules were added by other sources such as meteorites and comets
- Reactions could occur with hot, mineral-rich waters near volcanoes on the ocean floor
è This organic chemicals in Earth’s early oceans require nothing but normal chemistry!
Chemical Evolution
n  Thy greatest mystery of evolution of life is here!
How could the countless molecules floating in random patterns in the ocean
have organized themselves into a functioning and reproducing cell?
n  A number of creative ideas are helpful to give a key to solve the mystery
- Lipid molecules can form an oil slick on the ocean’s surface that might block the
Sun’s ultraviolet radiation. In this environment, polymers and other complex
molecules might have grown and diversified
à molecules break-up rate by sunlight << concentrated molecules grown-up rate
- The first cell may have evolved in a tidal pool lined with adsorbent (clay) minerals
à If a protected tidal pool is necessary for the development of life, then life may be
relatively rare in the universe
RNA enzymes – Chicken and egg controversy
n  You need DNA to make protein enzymes, but you need the proteins to make the DNA
è How could the first cell have solved this dilemma?
n  Attempted solutions to the question has one assumption: the very early life forms had
a rather different chemistry than today’s
n  We will be able to find a solution from studies of biochemistry
- Some kinds of RNA molecules act as enzymes for chemical reactions in additional to
their usual role as nucleic acids
- Some kinds of kind of clay or other inorganic minerals may have worked for chemical
reactions
- Chemistry involving RNA as an enzyme may have occurred in deep oceans
The first cell
n  One of the greatest mystery of modern biochemistry:
Why do living things today contain only 20 different kinds of amino acids?
è The characteristics of the first cell may give a solution to the question!
n  The characteristics of the first cell
: No competition – no predators, not other life forms to compete for their oceanic
environment
è By chance or perhaps, this particular combination gave them a competitive edge.
In other words,
some early cells contained only certain types of amino acids and they survived
and dominated on Earth, and today’s 20 amino acids are descendants of them
è These 20 amino acids are one of perhaps many chance events à “frozen accident”
n  Unanswered yet …
The Evolution of Human Beings
n  Human species: Homo sapiens
Scientific classification of humans
: Animalia Kingdom, Chordata Phylum, Mammalia Class, Primates Order,
Hominidae Family, Homo Genus, H. Sapiens species
n  Finding fossils of the oldest hominid is very important to know the origin of ourselves,
but exceptionally difficult for three main reasons
1. early hominids fossils are focused in Africa, 2. early hominid fossils bearing
sedimentary rocks were rare in that time in Africa
3. many early hominid fossils are
buried in politically not easily accessible regions
n  Our branch of family tree broke off from other branches of the family including
orangutans about 7-8 Million years ago
n  Australopithecus ramidus: midway in from between later hominids and modern
human species, 4-6Myr ago
Australopithecus afarensis: know as “Lucy” (named after Beatles song), 3-4 Myr ago
à Different genus from human species, but closer to humans than other primate
à Lucy family walked erect with brains of the size of a modern chimpanzee’s,
and they were typically less than 150 cm tall and may have been covered with hair
The Evolution of Human Beings
n  Homo habilis (“man the toolmaker”): first Homo genus, larger than Lucy with
a larger brain, found in East Africa, 2.5 Myr ago
Homo erectus (“man the erect”): the first to use fire, found in East Africa, Asia, and
Europe (Ex. Java Man, Peking Man), appeared shortly
after Homo habilis and lived until 500,000 yrs ago
n  Modern humans (Homo sapiens “ “) began to appear about 200,000 years ago
n  Neanderthal man: another type of human being
Characteristics of Neanderthals
- walked stooped over, knuckles swinging, and with thick brow ridge like gorillas’
- larger brains than those of modern humans
- had a complex social structure, cared for elderly and infirm members of their tribe,
and performed burials just like religious ceremonies
The Evolution of Human Beings
Invertebrates fishes
reptiles
Australopithecus
mammals
Homo habilus
Homo erectus
The Evolution of Human Beings
Homo sapiens
Mysteries and controversies from Neanderthal
1. How closely Neanderthals were related to modern human beings?
- Neanderthal as a subspecies of Homo sapiens à Homo sapiens neanderthalensis
- Neanderthal as our nearest relative à Homo neanderthalensis
è From recent study, their DNA sequences were revealed as markedly different from
modern human beings
More precise study on the DNA sequence of Neanderthals is needed
2. What happened to them?
From fossils in Europe, they flourished until 35,000yrs ago, then suddenly
disappeared coincidentally with the entry of modern Homo sapiens
Several theories to explain the disappearance
- Genocide by our own species
- Intermarried with our species à a certain percentage of our genes are Neanderthal’s
- Eventually disappeared by competition à They couldn’t compete with more
advanced newcomers so moved away from the desirable settlement locations What does the evolutionary hypothesis of human
beings tell us?
n  In the past, there were many different types of humans – many members of the
hominid family- on the surface of Earth
n  For whatever reason, none of them survived to today except ourselves
à The process of natural selection and extinction have cut off the family tree
leading to the modern human beings
Next lecture is on,
Science of Environment: Chapter 19
www.sci.hokudai.ac.jp/~epark/ekpark_e.html