Your essay is 297 words long, which is OK, and has an average of 18.5 words per sentence, which is a little high. Try adding some short sentences to increase readability and for more impact and variety.

I agree with Tommy and ChrisLuke that your essay has a good clear structure and good ideas. I would add more ideas however, particularly in the third paragraph.  I also agree with ChrisLuke that the first paragraph is ‘top-heavy.’  It’s 87 words long. In the limited time in IELTS, try to get to the point as quickly as you can, and try to keep introductions short -  around 50-60 words or so.

You wrote:

It is true that human beings have suffered from numerous wars through the stone age to modern society, and it is a fact that most of the leaders of those conflicts were male. Therefore, some people hold the opinion that it is the male leaders that led us to violence and wars. They also propose that our society should be governed by females in order to be more peaceful. However, in my opinion, there is no definite link between the historical conflicts and the gender of leaders. (87 words)

There’s nothing wrong with the vocabulary, ideas, or linking. I really like the parallels in the opening sentence (‘It is true that,’ and ‘It is a fact that’).  

Let me see if I can write a shorter version:

It is true that humans have suffered from wars since the Stone Age, and it is a fact that most of the leaders of those conflicts were male. Some people claim, therefore, that men lead us into violence, and that a society governed by women would be more peaceful. However, in my opinion, there is no definite link between conflict and the gender of leaders.

Not much change. It’s down to 65 words. I’ve removed a formal phrase ('hold the opinion that'), and I’ve changed one tense -  ‘lead’ instead of ‘led.’ I could make it shorter, but then I would be making too many changes to your style of writing.

Here’s a completely different version

Most wars throughout history have been started by men. Does this mean that a society governed by women would be more peaceful? I am not so sure. In my opinion, there is no clear link between conflict and the gender of leaders. (42 words)

This isn’t better or worse than your paragraph -  it’s just shorter. But ChrisLuke is right -  if an introduction looks longer than a body paragraph, IELTS examiners are going to go back and read both parts again with a more critical eye, because normally they would expect the opposite -  a short intro and longer body paragraphs.  Try to give them what they expect!

Word Choice/Word Form/Usage

You wrote:

In ancient times, conflicts between two men would usually be solved by fighting, which was kind of cruel.  →In ancient times, conflicts between two men would usually be solved by fighting, which was kind of cruel.

‘Kind of’ is a lazy expression we use in speaking. Avoid it in writing. It’s, like, totally unnecessary. In the sentence above, you can just leave out the entire phrase.

• men are easy to get angry →men get angry easily             OR       it’s easy to make men angry

Ideas 

In the second paragraph, I would try to separate the ideas more clearly. You topic sentence was

To begin with, I admit that men's human nature tends to be more aggressive.

This is followed by two-and-a-half ideas, or maybe three:

• Men fought in the past
• Men fight today
• Male politicians generally choose violence

I think another idea or a good example might add to the paragraph

Paragraph Three has two ideas

• Wars are not decided by individuals but by governments or parliaments
• Women have been cruel

The last idea is crying for an example! And by repeating ‘cruel’ you are missing an opportunity to show your vocab. You also say that they were cruel to their people, which is true but a little different from war against another country. I think what happened was that you avoided giving an example of a female leader deliberately just to be safe!

And I will do the same.

Thanks!

A big thanks to Tommy and ChrisLuke -  good suggestions. Tommy played around with your sentence 

However, in my opinion, there is no definite link between the historical conflicts and the gender of leaders

...and you can see in my suggestion for a rewrite of the intro that I did too, but in the end I kept 'the' before the word gender.   Alternatives might be:

• ...between gender and leadership   OR    
• ...between the number of wars and the leader's gender    OR    
• ...between a leader's gender and his or her propensity for war     OR  
• ...between leaders' gender and their desire for war

Overall, it’s a very good essay and very easy to read. Just keep intros short and try to have more ideas before you begin. Three in each body paragraph is a magic number to aim for. Well done.

anyway, i just wanna share my comments with you.

1. your first paragraph is a bit top-heavy , if you compare it with your last paragraph....

Therefore, some people hold the opinion that it is the male leaders that led(lead, cuz this is an opinion, isnt it?)us to violence and wars

2.it is not necessarily true that female leaders would result in a more peaceful world.

(hmmm..i believe  it is "something" that" results in", not "a person" can result in any consequence or whatever.,.)

3. I would like to refer to what Mr WriteFix called "formal standardized generic phrases and even hackneyed phrases" to make my opinions clear.

It is true that....

it is a fact that....

it is not necessarily true that....

there is no evidence showing that....

As a matter of fact,.......

and ......

they are not wrong but do not contribute to your writing....hmmm..i mean, you can use a few but do not chuck all into your essay.....

4. Lastly, restate your opinion in the last paragraph .....

I think your essay is great. I really like the structure in this essay.

Below are my comments:

"It is true that human beings have suffered from numerous wars through the stone age to modern society, and it is a fact that most of the leaders of those conflicts were male. Therefore, some people hold the opinion that it is the male leaders that led us to violence and wars. They also propose that our society should be governed by females in order to be more peaceful. However, in my opinion, there is no definite link between the historical conflicts and the gender of leaders.

To begin with, I admit that men's human nature tends to be more aggressive. In ancient times, conflicts between two men would usually be solved by fighting, which was kind of cruelty. Even in modern society, men are easy to get angry and sometimes you can see some people fighting with each other because of losing control. When it comes to making political decisions, males tend to use violence as the effective measure to solve problems.

Nevertheless, it is not necessarily true that female leaders would result in a more peaceful world. First, in modern government, it is not the case that any single person can make the final decision about starting a war. Usually, a large group of people such as members of congress would participate in the decision-making process. This would make the decision more rational. Also, there is no evidence showing that women would choose more peaceful measures when they have the power to use violence. As a matter of fact, there were some female leaders in history who were very cruel to their people.

To sum up, the gender of leaders is not the key factor that leads us to conflicts and wars. We should choose right leaders based on their virtue but not on their gender."

Overall, I think you include a wide range of grammar in your essay, and many error-free sentences. Keep up the good work !

Thank you so much for your kind advice on my essays.

Sometimes I want to give my own opinions to the essays written by others but I'm always afraid that my comments may not be correct...

Below is the essay I wrote this morning. It took me nearly 45 minutes. Can you give me some advice about how to finish an essay in time? I always can't finish the two tasks of IELTS writing in time.

Best wishes,

Helloworld

Throughout history, male leaders led us to violence and conflict. If a society is governed by female leaders, it will be more peaceful. To what extent do you agree or disagree?

It is true that human beings have suffered from numerous wars through the stone age to modern society, and it is a fact that most of the leaders of those conflicts were male. Therefore, some people hold the opinion that it is the male leaders that led us to violence and wars. They also propose that our society should be governed by females in order to be more peaceful. However, in my opinion, there is no definite link between the historical conflicts and the gender of leaders.

To begin with, I admit that men's human nature tends to be more aggressive. In ancient times, conflicts between two men would usually be solved by fighting, which was kind of cruel. Even in modern society, men are easy to get angry and sometimes you can see some people fighting with each other because of losing control. When it comes to making political decisions, males tend to use violence as the effective measure to solve problems.

Nevertheless, it is not necessarily true that female leaders would result in a more peaceful world. First, in modern government, it is not the case that any single person can make the final decision about starting a war. Usually, a large group of people such as congress would participate in the decision-making process. This would make the decision more rational. Also, there is no evidence showing that women would choose more peaceful measures when they have the power to use violence. As a matter of fact, there were some female leaders in history who were very cruel to their people.

To sum up, the gender of leaders is not the key factor that leads us to conflicts and wars. We should choose right leaders based on their virtue but not on their gender.