(part 1 of 2): Physiology
Before we discuss the concept of equality – and how it relates to men and women in Islam – we have to make an important difference. Many people who talk about equality understand that this should mean treating two groups exactly the same way. However, this is not always appropriate. People’s needs, powers, abilities and inabilities have to be taken into account and contradict a single standard that applies to everyone and only fits a few.
So we have to distinguish between superficial, procedural equality and real equality, which means justice. Most societies recognize that the important thing is not procedural equality, but justice that is adapted to the needs and living conditions of the residents. People prefer real justice over procedural equality in everyday life because we recognize that the first means real justice. We adapt our workplaces, schools and economic areas to those with disabilities. We recognize the need for social security contributions to help the impoverished in society while the rich have to pay taxes. We let those who are emotional in their lives encounter psychological or physical difficulties, deserve special attention and attention. All of this is part of true equality and justice.
men and women
When it comes to men and women, everyone realizes that there are innate, indisputable differences between men and women. They are not the same; Men and women are naturally different in different ways. Because of this, it is not logical to ignore these differences by using the same yardstick in matters where they do not have the same conditions. This may be procedural equality, but it is not real equality. For example, it would be unfair for a husband to suggest that his wife work as hard as he does when she is pregnant. Justice can be achieved by recognizing the burden of pregnancy and the need for the husband to act accordingly. There are obvious biological differences – men experience neither menstrual periods nor births, whereas women generally live longer and have fewer health problems in old age. The AARP Bulletin printed an article on eight health differences between men and women:
When it comes to health, the differences between men and women are becoming increasingly apparent, even outside of their habit of taking annual exams and required treatments. In the event that men need a few reasons to make an appointment with the doctor, they should consider the following points:
At 74.4 years, the life expectancy of men in the United States is only slightly more than five years lower than that of women at 79.8 years.
Cancer kills more men than women.
Of those who die from heart disease before the age of 65, 70% are men.
Sleep apnea may be a serious disorder in which breathing occurs repeatedly during sleep. It is also more common in men than women.
Four times more men die from suicide, the eighth leading cause of death in men.
50% more men than women develop coronary artery disease over the age of 40.
Men have fewer fever-fighting T cells than women.
In the centenarian age group, women outnumber men by 8: 1.
Men and women compete separately at the Olympic Games because of their physical differences. At the age of 18 the average man is 175.8 cm tall and weighs 72.4 kg, while an average woman is 162.2 cm tall and weighs 63.3 kg. Based on weight, men have 50% more muscle than women. The average heart of a woman is 25% smaller than that of the average man. Women carry around ten percent more fat with them than men. 
In language and social sciences, women usually have higher scores than men, while the reverse is true for math and science. Both genders have their strengths and skills. As for the psychological differences between men and women, an article headed: ‚Men and women really think differently‘ quotes a new neurological study:
Psychology professor Richard Haier from the University of California, Irvine, led a series of research with colleagues from the University of New Mexico. What they found generally shows that men have almost 6.5 times as much gray matter with which general intelligence is associated; in comparison, women have almost 20 times more white matter combined with intelligence. […] In human brains, the gray matter represents centers where information is processed, while the white matter is responsible for establishing networks with these information centers.
The results of this study may help explain why men and women excel in different roles, said co-author and neuropsychologist Rex Jung of the University of New Mexico. For example, men tend to do better with tasks that require more localized processing, such as math. Jung said, „Meanwhile, women are better at matching and inserting information from scattered regions of the brain with gray matter, which benefits them in languages.“ 
Another article published in Psychology Today describes the differences between men and women as ‚inevitable‘:
When it comes to speaking and hand movements that require motor skills, the brain of women seems to be organized in a very focused way compared to that of men. This may be related to the fact that girls usually speak earlier and are able to express themselves more clearly and also have more fine motor skills. There are also more right-handed women than men, and there is no doubt about that. But when it comes to certain more abstract tasks, such as defining words, the brain of women is more diffuse than that of men, although there is no difference in the general vocabulary between men and women.
[…] Neuropsychologist Marian Diamond from the University of California at Berkeley, comparing the bark thickness in male and female rats, found that the right bark is thicker in most age groups in male rats, while the left bark is thicker in females is thicker, but only in some age groups. (see „A Love Affair with the brain,“ Psychology Today, November 1984). […] The fact seems inevitable that men and women differ genetically, physically and in many important ways also psychologically. 
Modern psychological science continues to reveal the differences between men and women, be it just the obvious behavioral patterns, as trivial as showing an angry face in a crowd. In the light of such manifest differences between the different genders, it is highly inappropriate for men and women to want to play identical roles. As mentioned in a New York Times article on women’s health:
Contrary to feminists‘ principle that women can do everything men do, science shows that women can do some things better and that they have various biological and cognitive benefits possess towards men. Then again there are some things that women are not as good at. 
God created us with different but complementary strengths and abilities. A man doesn’t need to become a woman, or vice versa, to be successful.
 Eight Differences in Men’s and Women’s Health, Gaby Gollub. (Http://www.aarp.org/bulletin/yourhealth/Articles/a2004-02-17-8diff.html)
 Performance Moderator Functions for Human Behavior Modeling in Military Simulations (ADDENDUM) Adrenaline – Khat – Exertion, Chang Y Chung, Dr. Barry G. Silverman, Jason Cornwell. (http://188.8.131.52/search?q=cache:OYtYvD7FS3QJ:www.seas.upenn.edu/%7Ebarryg/PMF_Addendum1.doc)
 Men and Women Really Do Think Differently, Bjorn Carey, LiveScience. (http://www.livescience.com/humanbiology/050120_brain_sex.html)
 Male Brain, Female Brain: The Hidden Difference, Psychology Today Nov, 1985.
 The New York Times. (http://www.nytimes.com/specials/women/nyt98/21saga.html)
(part 2 of 2): Substantial equality between men and women
Islam recognizes that men and women have physical differences, but spiritually enjoy absolute equality before God. In the Qur’an and Sunna it is clearly and emphatically emphasized that gender has no influence on the reward or punishment in the hereafter.
“See, I will not let any work of the active among you be lost, be it by man or woman; some of you are from the others… ”(Quran 3: 195)
„But those who do what is right – be it a man or a woman – and who believe in it will go to paradise and will not suffer the slightest injustice.“ (Quran 4: 124)
“We will surely grant a good life to those who do right – whether male or female – and who believe. and we will surely measure such wages according to the best of their deeds. ” (Quran 16:97)
“Those who do evil should only be repaid with the same, but whoever does good – be it a man or a woman and is a believer – they will enter paradise; it will provide them with maintenance without being billed. ” (Quran 40:40)
“Truly, the Muslim men and the Muslim women, the believing men and the believing women, the obedient men and the obedient women, the truthful men and the truthful women, the patient men and the patient women, the humble men and the humble women , the men who give alms, and the women who give alms, the men who fast and the women who fast, the men who keep their chastity and the women who keep their chastity, the men who Remember Allah often, and the women who remember Allah, Allah has given them forgiveness and great reward. (Quran 33:35)
“O people. We have created you from man and woman and made you peoples and tribes so that you may recognize each other. Verily before Allah is the most respected of you who is the most feared of God. Surely Allah is All-Knowing, All-Known. ” (Quran 49:13)
Thus, Islam clearly states that men and women have the same status and value before God, and only piety alone distinguishes an individual from others.
From a legal and practical point of view, the general rules for men and women are the same. Both perform the same acts of worship, obey the same Islamic decency and behavior, and are subject to the same legal punishments. But there are also many cases that are regulated differently. Women are exempt from prayer and fasting during their menstruation. Men are prohibited from wearing gold and silk, while women are allowed to, because it is in the nature of women to make themselves beautiful. Friday prayers are mandatory for men but voluntary for women. Men have to spend their money on the family, but the woman’s money belongs to her alone, she can spend what she wants. There are also differences in clothing regulations, because the physical appearance of men and women is also different. All of this reflects the natural differences between men and women. In less legal matters, Islam treats men and women according to their predispositioned differences, as it complies with substantive (actual) equality and the interests of justice.
We come to the conclusion that Islam reaffirms the absolute spiritual equality of men and women and awards both the same rank before God. In legal matters, Islam represents the substantive equality of men and women, recognizes their unique strengths and abilities, and acts accordingly by protecting the rights of both.