Have Men Evolved to Detect and Respond to Cues of Ovulation?

By Sarah Raines, Ryan Casey, Tori Blair, and Chasity Ramsey

Fellas, have you noticed that you find your girl to be more attractive at certain times in comparison to other times? Ladies, do you occasionally find that your man seems to be overly drawn to you more than usual?  If you answered “yes” to one of the questions above, you aren’t alone. It might surprise you to learn that this “yes” speaks to research supporting the hypothesis that men have evolved the ability to detect and respond to different cues of ovulation

                                                         Ovulation and Evolution

Ovulation occurs when an egg is fully matured and released from the ovaries to be fertilized by sperm. This normally happens once per month, about midway between your last and next period, and it is only in the days surrounding this event that it is possible to get pregnant.

Ladies, how many of you know for certain when you’re ovulating? If you’re like many women, you may not be sure. So, if you don’t know when you’re ovulating, how could ovulation possibly impact your behavior, or your partner’s perception of you? As it turns out, neither women nor men need to know when someone is ovulating in order for ovulation to matter. There is a possibility that you do not know when you are ovulating because you do not notice when your body is going through its hormonal changes, but it is, and those fluctuations have noticeable effects–if you know where to look.

Unlike humans, some female animals show obvious signs when they are in “heat” and ready to look for a sexual partner. This is known as Estrus or Oestrus. Sheep, lions, dogs, baboons, and other animals all show signs of being in heat when they are ready to mate. Some of these animals’ butts turn red when they are in “heat” and that lets other animals know that


they are “ready for action”.  Not all animals have pair-bonding between mates so they encourage male conflicts and competitions to determine who they will mate with.

So, why don’t humans have these more obvious signs of fertility? One possibility is that it’s due to the highly social nature of our species. Concealed ovulation in humans has opened the door for stronger pair-bonding. For instance, in some species, males and females only affiliate with each other when it’s time to mate–the rest of the time, they do their own thing. But in other species, like ours, male-female bonds are longer-lasting. Concealed ovulation might promote these longer bonds because neither partner “knows” when sex will lead to a fertilization, and so they have sex across the cycle. Stronger pair-bonding would increase male investment and it could also increase male-male cooperation. It also helps prevent men from fighting with one another for women in estrus. (Besides, I am sure you ladies wouldn’t want to walk around with bright red butts to attract men, would you?)

There have been researchers who hypothesized that ovulation was concealed in humans because it helps women and men form long-term relationships that would reduce men’s chances of looking for another mate. This would have benefits for both men and women: women would receive more investment from men to help care for their children, and it would also cause men to have higher confidence levels of paternity, because they would be with their female partners across the cycle–which leads into our next question.







Why would men need to detect cues to ovulation?

Ancestral men who could identify and attract women who were high in fertility gained more reproductive success over men who were unable to detect fertility. So not knowing when females are ovulating may have decreased the likelihood of our male ancestors of having offspring because they couldn’t respond to females obvious oestrus cues that signal when women are most fertile. This suggests that there would have been an advantage for men who could detect subtle cues that women were ovulating. In other words, if the subtle shifts that women go through during ovulation caused some men to find then more sexually attractive, these men would have been more likely to father children, and would have passed the genes for these preferences on to modern humans. 


What are the subtle cues to ovulation in humans? 

Clothing Choices

Ladies, imagine you are going out for a night on the town and you need to get dressed. What are you mostly likely to choose right now? Shorts and a low cut shirt or skinny jeans with a nice shirt? Maybe a short dress with some high heels or a long flowy sun dress? According to some research, your answer might depend on whether you’re ovulating.  According to Kristina Durante’s study on sexual cues during ovulation, women who are ovulating are much more likely to choose shorts and a low cut shirt or a short dress with high heels than the more conservative clothing.

We also see that both men and women are able to notice this shift. In an evaluation done using pictures of women, 94% of women and 86% of men correctly chose the woman who was closer to ovulating; under the only criteria of, who looks more attractive? This subtle “cue” can show men that you are sexually available, mature or just have a simple ability to reproduce.

Facial Changes

Another study that discusses attractiveness is from Roberts et al. and it states that women’s facial attractiveness may vary and change over the course of their ovulation cycle. The article suggests that the visible cues to human female ovulation are primarily in the face and that this paired with other topics discussed in this post will pair nicely to make our cycles less cryptic or hidden. The results of their study showed that facial attractiveness does vary throughout the ovulation cycle and it can be seen by both men and women. The changes to the face that can be seen, are often clearer skin or a subtle redness to the face, often called a blush.

Image from Roberts et, al.

When looking at the picture to the right, which do you find to be more attractive? If you chose the two left versions then you picked the two that are ovulating. The change that is seen in the pictures are subtle and caused the effect to be minimal. Although, according to researchers, with other “cues,” changes in the face may be significant enough to show ovulation. Note that such possible attractive facial cue features are dilation of the pupils, both the size and color of lips, and skin color and tone. 

Though both of the above studies suggest visual cues to female ovulation, there are other subtler cues, such as smells and voice changes, that suggest ovulation.

Vocal Attractiveness

There are some existing studies on the singing voice changing throughout the ovulation cycle, but in the study discussed here the researchers carried out a review of six different English studies on the same subject and came to the conclusion that because of hormone changes during ovulation, the voice can vary in volume and pitch, which does cause a slight voice change throughout the ovulation process.

 A study that tested if women’s voices changed found that men prefer higher pitched voices rather than lower pitched voices. They also found that when women are ovulating, they speak with a higher pitched tone. This cue to ovulation has been shown in few studies, but it does show that men can hear a difference in pitch and that that difference can make a woman more attractive.


The Scent of a Woman

Smell is a strong sense. It is said smells are the fastest way to transport us back to memories. But can we as humans smell ovulation? If you aren’t convinced that behaviors are different when ovulating, there is even more evidence ovulating woman actually smell different to men than non-ovulating women–and furthermore, there’s evidence that this detection influences testosterone levels.  Testosterone can cause many changes in males, whether there is a large increase or a small one there can be many differences. Innately, the testosterone levels in a man can increase when doing nothing but smelling women’s shirts. Seems strange, but true, and there is more! Not only did the testosterone levels increase when sniffing shirts worn during ovulation, but decreased when sniffing the shirts worn by non-ovulating women.


So why is this increase in testosterone beneficial? Increasing testosterone in males has been linked to an increase in sex drive and overall desire. Therefore, an increase in testosterone when smelling a shirt is a great cue to the innate changes that occur in men when a woman ovulates. This is yet more evidence that evolution is pointing men in ways where ovulation can be pinpointed.

Pretty cool evidence, no? But there are other ways that future research endeavors can provide evidence for men having evolved to detect and respond to cues of ovulation.


Okay, so here’s what we covered!

  • Women’s dress, facial appearance, perhaps voice pitch, and smell seem to serve as cues of ovulation for men.
  • Fluctuations in testosterone as a result of smell seem to be indicators of men’s ability to detect of ovulation.
  • Evolving to pick up on these proposed ovulatory cues increased our male ancestors’ likelihood of having offspring and, therefore, they past those abilities onto us.

And now that we’ve got that covered, here’s what future research can do to add to the body of evidence behind men evolving to detect ovulation.

What’s next? Future Research Directions for Ovulation

Since women express a preference for clothing that will draw more attention or is less conservative, researchers could have women come in at ovulating and non-ovulating times to try on an assortment of more or less conservative outfits.  This would strengthen research because women trying on outfits would mean that their final choice in outfits would most likely result in how the outfits make them feel at low and high fertility times. 

Expanding on the above,  it speaks to the second study mentioned in which participants reported on how much the women cared about being perceived attractively. Researchers could compare the reports on how the outfits make women feel to the ratings done by those indicating how attractive the women want to appear.

Reflecting back to the study in which participants noted the change in women’s faces at ovulating and non-ovulating times, in order to strengthen these findings, it would be good if future researchers had women come in to have photographs taken over the course of several ovulating and non-ovulating times and be able to expose the judging participants to several versus two pictures of women.       

Now, for the changes in voice pitch that women seem to undergo at ovulation, the best case for strengthening the evidence here is for researchers to look for voice pitch changes and men’s attraction to it in multiple contexts. Findings from multiple contexts would be good because a smaller likelihood of factors potentially characteristic of just a few contexts would be affecting the overall body of evidence.   


And the same is probably true for strengthening the evidence behind men picking up smell as a sign of ovulation. In other words, why not have men smell women’s jeans, bras, or even hair accessories such as headbands? 

And what about a study that represents ovulation cues being detected over time? Researchers could administer weekly email questionnaires to men to report on attraction to their wives/cohabitating partners. The types of questions asked of participants would inevitably relate to actions/behaviors (e.g. choice in dress and so forth) and voice and smell. 

Well, that’s all folks!

Bet you’ll never look at an attractively dressed woman quite the same as you once did before.


It’s Evo-Lit-ionary: Why Humans Like Drinking Alcohol

By: Luke Harbison, Maddie McCall, Nicole Moughrabi, and Adora Nguyen

It’s no secret that many (if not most) people like to drink — fruity wine coolers, a cold beer, some mixed concoctions that are most definitely shaken, not stirred. But, why? Especially considering that alcohol itself is bitter, toxic, and leads to us being vulnerable and making poor decisions, there must be some scientific reasons other than having fun while losing inhibitions.

And there are — alcohol has been utilized as a medicinal tool, a way to find pleasure and feel good, and as it turns out, our widespread preference for alcohol may even be a byproduct of an evolved adaptation.

But before we get too much into evolution, let’s take a quick look into how alcohol has been used in more recent times.

Medicinal Alcohol


One interesting historical use of alcohol was medicinal. For instance, in Ancient Egypt wines and beers were often used as forms of medicines that could help with a wide-range of ailments: a beer mixed with coriander, bryony, flax, and dates could ease stomach problems; coriander mixed with fruit and beer could help with blood in someone’s stool; salves for herpes were created from coriander, seeds, myrrh, and fermented honey. Alcoholic ingredients were also used as laxatives, emollients (which are soothing lotions for your skin),  and even  aphrodisiacs. In short, alcohol was a key ingredient in healing during ancient times.

But, most of us aren’t living in ancient Egypt, and we can just run to the closest pharmacy to pick up our (much more effective) meds instead of making them ourselves. Why do we still continue to drink alcohol?


One explanation is that we’ve evolved to like the feeling of being drunk (or at least tipsy, for those who might only indulge in a glass of wine once a week). One clue that this might be the case is that alcohol stimulates reward circuits in our brains. When we consume alcoholic drinks there are many chemical reactions happening, namely the release of dopamine, which helps us to feel good. This release of dopamine happens in the nucleus accumbens, which is just a fancy name for the reward center of our brains. In short, alcohol can help us feel good. It helps us relax, offers us a way to connect with others in social settings, and can enhance the food we’re eating. But why does it make us feel good?

Some researchers have argued that the hedonic (or pleasurable) qualities of a stimulus (like food, or water when you’re really thirsty, or sex) are indicators of its “fitness goodness,” or in other words, whether something will help us survive or pass on our genes. Animals who found pleasure in “fitness good” stimuli were therefore more fit than those who didn’t (evolutionary speaking, meaning better able to survive, reproduce, and pass on their genes — not necessarily able to lift weights). This means that animals that sought out those pleasure-rewarding stimuli were overall more successful than those who didn’t. So, the fact that alcohol feels good to us suggests that alcohol–or something associated with alcohol–might have actually been good for our ancestors’ fitness.

Before we get to what that “something good” might be, though, it’s important to point out that this reward mechanism can go awry, which in the case of alcohol and other dopamine-stimulating drugs, it certainly can. There are some studies that state alcoholism can be considered an “evolutionary hangover” of this reward mechanism. Over time, humans have become very skilled at seeking out pleasurable stimuli over more important or necessary things, such as food or water, which is a not-so-good thing.

The Genetics of Alcoholism 

There are multiple studies that put forth the argument that certain genes were evolved to help with the breakdown of ethanol and metabolize alcohol–another clue that alcohol is a part of our evolutionary past in some way.


However, consuming too much of ethanol can have great risk, considering that these specific genes can also influence a person’s risk of becoming an alcoholic. Various alleles (or versions) of these genes may determine the likelihood of someone developing alcoholism based on how they break down ethanol. In short, two people could drink the same amount over a span of a few weeks, but the person whose genes are more inclined to addictive behaviors and efficient breaking down of alcohol runs the higher risk of becoming addicted. It is likely, based on these and other studies, that these genetic risks are at least in part explained by how rewarding people with different gene variants find the consumption of alcohol.

Risk Taking Behavior

Furthermore, other studies have shown that an important behavioral predictor of alcoholism is tied to one’s levels of impulsivity; the more impulsive someone is, the greater chance of excessive consumption of alcohol and, ultimately, alcoholism. Impulsive behaviors may arise from genetic properties or can be influenced by social factors. Thus, alcoholism is not thought to be caused by one element, but rather a combination of various genetic, behavioral, and learned traits (it’s nature AND nurture — no “vs” here).


We humans also have a tendency to start drinking at a young age, possibly even younger than certain laws may allow for. This may be due to alcohol being a (literal) forbidden fruit; some studies have shown that adolescence is the time in which behavior prohibited by authority seems enticing (i.e. underage drinking). Adolescents see themselves as being invincible and unafraid of the unknown, which prompts them to actually seek out certain ambiguities — such as underage drinking.

As you can easily guess, underage drinking is not really a good thing to do; not only is it illegal in some societies, but it can also hinder brain development, considering the brain isn’t fully developed until you’re almost 30. So while drinking alcohol can make us feel good, there are very real dangers that come with drinking.                                                                                                                                                                     

Which brings us, finally, to what evolutionary psychologists consider the underlying cause as to why humans like drinking alcohol: for our ancestors, it all came down to food.

Ripe Fruit and Digestive Fermenting

A major challenge our ancestors faced was obtaining enough food, and food that wouldn’t be dangerous to us. A solution to this problem was to evolve taste preferences that helped us determine which foods offered the most calories and aversions for things that were toxic. For example, humans tend to enjoy rich umami tastes, which are associated with foods rich in fats and proteins, such as meats. In contrast, we tend to avoid very bitter tastes, as bitter foods tend to contain compounds that are toxic to us.

We also like sweet tastes, which are associated with high-sugar foods, such as sodas and cakes in modern times. This sweetness preference is why our ancestors feasted on delicious, ripe fruit (the closest thing to cake that they had available)… which also just happened to have high levels of ethanol. This also answers the question as to why we enjoy a drink that can be so bitter. Because it wasn’t always so bitter — it used to be sweet and fruity.

This main hypotheses that explains why we enjoy alcohol is called the Drunken Monkey Hypothesis. By studying monkeys, who are our closest evolutionary relative, we find that their diet is predominately plant-based; this supports multiple pieces of evidence that our ancestors also ate many plants. But while monkeys often times seek out ridiculously ripened fruit because of their high level of calories, those fruit also have high levels of ethanol (reaching 1%), which then ferments while digesting, and ends with the monkeys becoming drunk. This can also happen to any animal that eats the fruit, and below is a video of a bunch of animals who hopefully have their own DD.


But notice that the animals go after the fruit because they are ripe and have high levels of calories — becoming drunk only happens coincidentally. This is called a by-product, or a secondary characteristic that gets carried along by an adaptation, which is the actual evolved solution to a survival or fitness problem. So in this case, our ancestors faced the problem of selecting the very best fruits to eat, evolved a preference for sweetness that solved this problem, and coincidentally, also developed a taste for the ethanol that was also in the ripe fruit.

Take Aways

There are many reasons as to why modern-day humans enjoy drinking alcohol, and if you ask anyone you’re almost guaranteed a few of those answers. However, alcohol has been used for more than just drinking. Just to recap:

Alcohol was once used in ancient medicines that would solve an assortment of ailments (although, today the main ailment solved by alcohol is social anxiety or a stressful job).

But as far as researchers can tell, the deeper evolutionary reason as to why we drink is because our ancestors feasted on ripe fruit whenever they could get it, and their taste for fruit carried on to us. Our drunk cousins, the monkeys, can demonstrate this with their penchant for alcoholic fruity drinks.

Which can unfortunately lead to large amounts of consumption, potentially resulting in alcoholism. Different genes and chemicals are used to breakdown alcohol, but these genes and chemicals can also determine whether or not someone is more likely to become an alcoholic.

When it comes to drinking alcohol, no matter the reason why or how, it is important to be safe and be smart. Remember, it’s survival of the fittest — not the survival of the drunkest!


Jealousy: Successful Tactic or Harmful Emotion?

By North Angle, Cristoni Couvrette, and Anne Mette Rasmussen


Imagine you’re sitting at home scrolling through some sort of social media platform (whether it’s Facebook, Instagram or snapchat) and you see that your significant other has been commenting (or posting) flirtatiously with his/her hot coworker. How do you feel? Most people would immediately feel a sense of possession overcome them when they see their partner’s attention focused intently on someone else. Jealousy is an extremely strong — and surprisingly old, in an evolutionary sense — emotion.

Even though modern attitudes about relationships have become significantly more flexible, jealousy is still a common part of our love lives. Whether people are swingers, friends with benefits or serial daters, jealousy is commonly found. This powerful emotion can inspire songs, strengthen a relationship or even prevent a relationship from ending. However, the same emotion has the power to cause a breakup, inspire hatred, or result in serious harm.

But why do we get jealous? In this post we’ll explore this question from the perspective of evolutionary psychology. We’ll explore the adaptive benefits of expressing jealousy, the gender differences in jealousy, and lastly the benefits and setbacks that jealousy gives romantic relationships today.

Why do we get jealous?


Jealousy for many people is recognized as an undesired emotion that can trigger unflattering and unwanted thoughts and behaviors. Although unpleasant, evolutionary psychologists hypothesize that jealousy has been a beneficial solution to the problems that our ancestors faced. More specifically, jealousy is hypothesized to be a solution to mate retention. Ancestral men and women needed to retain their mates in order to reproduce successfully.

Mate retention can be threatened in various ways, for instance mate’s infidelity or mate poachers that try to “steal” one’s mate for either a one night stand or for a long-term relationship. These threats have constituted problems for ancestral humans recurrently, which is why evolution in response has selected defenses that minimize these problems.

Jealousy is hypothesized to be an evolved adaptation that helps retain long-term mates by averting mate poachers (e.g. curtailing your partner’s contact with potential rivals and fending off rivals who show interest in your partner) and deterring mate’s infidelity (e.g. show vigilance to circumstances in which your partner might be unfaithful and furthermore increase own efforts to fulfill your partner’s desires so that he/she is less likely to cheat). Ancestral men and women that did care about or could detect threats to mate retention would have had a reproductive advantage over those who didn’t. Therefore their genes were passed down to future generations in a relatively greater frequency. Eventually, they passed down the genes associated with those traits along to modern humans. However, the specific situations that trigger jealousy are hypothesized to be different between genders.

Men and Women differ in the cues that trigger jealousy


Men and women that fail to retain their mates are faced with different problems when it comes to survival of their genes. Because of these differences, they tend to react differently towards situations that trigger jealousy. For men, there is always the risk of paternity uncertainty (not knowing whether the child is his or not). A woman, on the other hand, is 100% sure that the baby she is carrying is hers. This in turn brings up the possibility for cuckoldry –- that is, the risk of investing resources in another man’s child. Evolutionarily, cuckoldry would have posed a great cost to ancestral men, as they would have been giving up other mating opportunities in order to raise a child who wasn’t genetically related to him. Thus, men are predicted to be more sensitive to cues of sexual infidelity (when a partner pursues sexual interactions with another individual). By evolving mechanisms that are sensitive to sexual infidelity, he is protecting his ability to produce and invest resources in his own biological children.

Ancestral women, however, faced different consequences of infidelity. Because women must invest more biological resources in producing and raising children (e.g., carrying a baby to term, nursing, and so on) than men, our ancestral mothers selected male mates according to who was willing and able to invest in children in other ways.  If a woman lost her partner to infidelity, this meant that she also lost her partner’s time, attention, energy, and resources for both herself and their child(ren). The loss of his commitment would have had great implications for both her and her child(ren)’s survival. Thus, women are predicted to show a greater sensitivity to cues of emotional infidelity (when a partner forms a deep emotional connection with another individual), because this carried the risk of losing her mate’s resources to another woman.

These sex differences have been observed in a study conducted by, Buss and colleagues (1992). This study asked both men and women to choose between two very upsetting events: (a) their partner having sexual intercourse with someone else or (b) their partner falling in love with someone else. Now of course these situations are incredibly painful for both men and women, but in a “would-you-rather” situation there tends to be a common sex difference between men and women. It turned out that 60% of men found sexual infidelity more upsetting, while 83% of women found emotional infidelity more upsetting.

Not only is jealousy expressed as an emotional reaction, but it has also been shown to directly impact behavior. One study found that males responded with more anger, greater likelihood of relationship dissolution and less likelihood of forgiveness in response to sexual infidelity compared to emotional infidelity.

These sex differences are found consistently across different cultures. Buunk, Angleitner, Oubaid, and Buss (1996) found similar gender differences within the American, German, and Dutch cultures. Because values in the German and Dutch cultures de-emphasize sex differences and have more relaxed attitudes about sexuality compared to America, studies like this one provide particularly strong evidence for these sex differences being more than the result of learning, and thereby speaks strongly for the evolutionary psychological hypothesis. In short, because men and women have faced different adaptive problems caused by a mate’s infidelity (paternal uncertainty vs. diversion of resources), the sexes show differences in cues that trigger jealousy.

Jealousy: benefit or setback today?

In conclusion, jealousy is an evolved emotion that serves an important adaptive solution. Jealousy aids mate retention by causing behavioral tactics to fend off mate poachers, deter a partner’s sexual infidelity, and help retain long-term mating practices.


While too much jealousy can cause a relationship to end, or in extreme cases, even result in spousal abuse. However, jealousy is not all bad. Imagine being in a bar with your significant other. An attractive stranger approaches you, compliments your looks, and starts a conversation. There is no doubt that he/she is flirting with you. Your significant other is not bothered at all. He/she let’s you continue the conversation without interruption and might even take a seat to give you some privacy. How do you feel? Do you appreciate his/her open-mindedness or do you get upset by their lack of care? Most people feel hurt, and wish that the situation would provoke jealousy in their partner. In this case, jealousy can be very beneficial, because when shown in moderation it can be used to ensure greater commitment from a partner, increase psychological closeness and test the strength of the relationship.

Overall, jealousy is an influential emotion that can be either constructive or destructive in romantic relationships depending on how aggressively it is expressed. We should keep in mind that jealousy isn’t just a primitive feeling we’ve carried on through generations of humans; it serves to support mate retention tactics and behaviors that arise when situations such as mate poaching or a partner’s infidelity threaten to end a relationship.

Although men and women experience jealousy in different forms and for different reasons, they do share a similar goal. Ultimately, jealousy served the same purpose for our male and female ancestors alike: It helped them recognize and navigate problems in the wonderful world of mating.