why are girls more picky about who they sleep with?

in general men seem to be ok with the concept of sleeping around / having sex with many girls but girls on the other hand are more reluctant to do the same. of course there are social reasons for this. reasons such as the social domination of females by males. if we look at the world right now, we can see female sexuality which changes a lot from one part of the world to another depending on how "evolved" the society is. you would see much more sexually liberated women in countries which rate the highest in gender equality.
but there are also evolutionary reasons for this difference in this behaviour between the genders. the reason is that when a women would mate and get pregnant, it would take her atleast 9 months to 1 year to be able to have an opportunity to make that choice again. the male on the other hand can make that choice of choosing his new mate in a matter of few minutes. so, every time she has sex the female is making a choice which has a much bigger impact on her life compared to the male and hence she would always act more choosy. but this evolution happened in the our long history when we didnt have condoms and other birth prevention tools. given how easy it is to avoid pregnancy now, i think this evolution would roll back and we would see similar lack of pickiness from women as we have seen from men for so long

why do we cry

the non-emotional reasons we have tears is to keep our eyes clean and hydrated .. so you would have tears in your eyes when there is a foreign element which enters your eyes .. thats the way the human body protects the eye ..

the other kind of crying is what babies do ... atleast the vocal part of the crying is related to the lack of communication skills of the baby .. also crying was a way to ensure that the baby can reach its parents in case they are separated (which i assume wasn't very uncommon when we were wild) 

now the more complicated kind of tears .. the one which we get when we get too emotional .. there is one evolutionary reason for the same.. its old people copying the babies .. most adults have an urge to show sympathy to anyone crying (because they associate crying with babies and adults are wired to take care of babies) .. so when attacked or under distress humans would start crying to mimic babies which increased their odds of being spared ..

why do guys masturbate

is there an evolutionary reason to this? first of all, its not just humans who masturbate.. there are bunch of animals who do it .. dogs hump all the time .. horses do it as well ..

now going into the possible reasons .. one reason which is proposed in general is that it is the process to get rid of old semen in the body to be replaced by freshly produced ones which would have higher odds to fertilise the egg ..

or may be this is our way of fighting evolution .. humans were sexually polygamous where in a male would mate with a group of females .. in the recent past we have moved from sexually polygamous to being socially monogamous .. and may be masturbating (by watching porn or fantasising about different women) is a way of men to stay faithful to their partners while satisfying their need to be sexually polygamous..

or may be the only relation of masturbation and evolution is that the former is the product of sexual urge and the latter needs sexual urge to succeed ..

skin colour and evolution

how was the skin colour of different races driven by evolution?

earliest sapiens (current humans) started from Africa .. Africa has ample amount of sunlight and given we never wore a lot of clothes (or had sunscreen) to protect ourselves from sun we needed melanin .. its a natural skin pigment which protects skin from UV radiation and hence cancer .. so we in Africa produced a lot of melanin to survive .. then when the sapiens moved to north in Europe the exposure to sun was much lower which lowered the need of melanin giving them a fairer skins over tens of thousands of years .. then the same europeans moved to south america via north america the melanin went up again giving them back the darker skin colour ..

why do older guys go for younger women

why do we see so many not-so-young men leaving their wives and families for young girls ..

as usual .. i would blame evolution instead of calling the guy a pervert .. all a guy wants (without him knowing) is to ensure that his gene goes on .. he wants to maximise the probability of having kids ..

there is a big difference between male and female fertility .. females reach their peak at the age of 20 and their fertility goes down very fast after the age of 35 .. same thing is applicable to males as well but the decline in fertility is not that pronounced .. this is also because the male just needs to fertilise a healthy egg but the female has to go though a much longer 9 month gestation period which requires her to be in top health conditions ..

so our ancestor males figured it out that if they want to maximize the probability of their gene's survival and have more babies they need to move to younger female partners once their current partners reach a not-so-fertile age of 40 and above .. this tendency of moving to younger girls has lived on deep inside the males long after till today .. its natural instinct that a guy in his 40s would get attracted to a girl in her 20s .. this is one of the reasons we as a specie have survived .. if it wasn't for this our chances of survival would have been much lower

why do guys like girls with big boobs and ass

the definition of sexy is surprisingly well defined all over the world .. it has been changing off late but still a girl with curves (big boobs small waist) is the most common standard for sexy

there is a hormone called progesterone which is vital for female pregnancy .. helps in maintaining menstrual cycles and supports gestations .. there is another hormone called estradiol which helps in development of sexual organs (supports vagina lining etc) ..  now it has been researched and found out that the the girls with a high ratio of boobs to waist would have as much as 3 times of these hormones than other girls .. 

us humans had obviously figured it long time back by trial and error .. the guys figured out that if he could find a mate with a high ratio of breast to waist, his odds of procreating would go up a lot .. this was learnt by human males over 100s and 1000s of generations and has become a part of the way guys think now without anyone having to tell them .. 

and thats why a guy would get attracted to a "hot girl" with big boobs / ass and small waist :)

why are most people right handed

humans are different from most other animals in this .. most of us (close to 90%) are right handed .. but is there any evolutionary reasoning

humans started using tools very long ago (the oldest stone tools found are 3.5 million years old !!) .. we started sharpening stones to make axes / hunting gears / hammers etc etc .. but such tools would have been a prized commodity to be used by a group or a family .. there would be less tools than users .. most of the tools worked better in one hand than the other (try asking a left handed guy to use your scissor and you would know), which means that it's more efficient for the group as a whole that everyone is better at using the same set of tools with one hand .. now i can't think why right would be preferred over left in evolution so i just assume it was 50:50 odds.. so more and more people became so that they could use the same set of tools which leaves us where we are now..