Presentación en inglés para trabajar la interacción entre la reproducción sexual y la evolución de las especies.

1. M.J. Morales

3. Why sex?
The secret of
survival is sex.
Sex propels
evolution and
evolution
propels sex.

4. Why does life need sex?
 700 millions of years ago, simple single-
cell organisms reproduced in an asexual
way, forming identical copies of themselves,
and transmitting all their genes.
 Many studies show that there are lots of
species in nature that can reproduce without
the participation of two genders, in
particular without the male. Ex. Lizard in
Texas

6. There has to be some
fundamental biological
evolutionary reason for
sexual reproduction.
The case of the fishes in the
desert of Sonora, in Mexico.
The Red Queen Theory:
‘Evolution is a race’.
If all the genes were shared,
so would all the weaknesses.

7. The origin of sex: a casual
meeting which resulted
successful.
The two strategies:
 Quantity versus quality.
 Speed versus nutrients.
The war between sexes.
Fewer egg means less chance to
pass your genes and therefore,
females do better being choosy.
 It explains a lot about how
species evolve, and why they look
and act the way they do.

8. Natural selection versus Sexual Selection
If Natural Selection is operating on all organisms the
same, why is it that, in nature, you can see differences
between males and females? There must be a reason.
Some scientists support another idea advanced by
Darwin: the Sexual Selection Theory.

10. Big eyes, beautiful singing, bright colors, big horns, long
necks, etc., they are all examples of the most useful things
to attract females, but in some cases of natural selection,
they provoked the extinction of species because the
females’ tastes conditioned the daily life of males.
An example is the extinction of the Irish elk.

11. The following question is…
Then, have females
controlled the evolution
through their choices?
According to the Sexual
selection Theory, males
usually compete for the best
opportunity to mate, and
females choose the best genes
for their progeny.
However, sometimes it’s
important to pay as much
attention to behavior features
as to physical ones.

13. Evolution has favored many
species in which male and
female share de role of
parenting.
The result is monogamy: a
social solution to a biological
dilemma.
Nevertheless, … females
sometimes cheat. (In some
migratory birds, 40 % of all
chicks are not descendents of
the males that feed them).

14. And, what about
humans?
Sexuality in primates is more than fertilization, it
became a way of communication and socialization
in a community.
That behavior prepared the basis for the human
reproduction. In our case, all began some few million
of years ago, when we went down the trees and we
became bipeds.

15. Some anatomical changes in the
pelvis and sexual organs were
required, but the most important
step in terms of sexuality was the
growth of the brain.
According to some scientists, the human brain grew so
much that humans had to do a shorter pregnancy, and,
as babies were less mature at the moment of birth, the
relationships had to be stronger and durable.

16. This change
supposed the
birth of love.
We needed a long-
lasting union with our
partner, and it affected
our anatomy,
developing an area of
the brain totally
devoted to love.

17. Some studies carried out by
evolutionary psychologists
show more things about
human reproduction.
For example, we are able to
recognize the amount of
genes that results more
different from ours and,
therefore, they are better in
order to introduce variability
in our offspring, and it’s
amazing because we do it just
by smelling.

18. Moreover, females choose more
masculine characteristics for a
short term relationship (trait of
high testosterone levels),
whereas we choose softer faces
for a long term relationship, and
more than that, we change our
choice at different moments of
our menstrual cycle.

19. It’s clear that our choices
have conditioned our
evolution and they remain
doing it. More than that, we
don’t do these choices only for
beauty but for the brain too.
Ex. Cyrano de Bergerac.
Evolutionary psychologists
say that our cultural
expressions are part of a
reproductive strategy. This is
a controversial theory.

20. Finally, we must think
about another
question…
Humans changed sex forever by including love, and
now we are taking a farther step, taking our own
evolution in our hands, and isolating this one from
sex.
Sex became futurist when humans could create other
living beings in a Petri dish.
What about the future of sex and
human evolution then?

21. Some scientists tell us that, in the future, human evolution
will be conscious, and it will be irresponsible to leave the
extremely important process of conceiving a child to chance .
Is it possible that humans forget millions of years of
natural evolution in order to control the future of the
species?

23. Bibliography
http://en.wikipedia.org/wiki/Evolution_of_sexual_re
production
The evolution of sex
https://www.youtube.com/watch?v=wxysZmNsyDk
Evolution Why sex?
https://www.youtube.com/watch?v=89rQDlx5MXA
El sexo en la evolución
https://www.youtube.com/watch?v=EAver-bRjEg