Introduction

One of the most important factor in the success of genetic research projects is the well-defined samples collection criteria. Some studies may depend heavily on how homogeneous the selected control or /and the affected group.

The 100 Arab human genome project is no exception. The main goal of this project is to study the Arab populations variations at the level the genetic makeup. One major obstacle to achieve this goal is heterogeneity of the Arab populations.

So, who is Arab?

There is no direct answer to this question. We can use 3 different classifications of Arabs as following:

Political:
Arab league is located in the Middle East and include 23 different countries. Total population is around 340 million plus. (see table no.1)

Lingual:
To some, any one who speaks Arabic language is an Arab. This increases the number of Arabs since there are many people around the world who speak Arabic language (e.g. in central Africa, central Asia,etc).

Ethnic:
This is the most relevant classification for genetic studies in general. The Arabs are originated from 2 locations based on historical references to form two major groups.

• The first is called (Arab Aarbah: Qahtan or Jaktan in The Bible العرب العاربة) means the ‘the original Arabs’. They are roughly 50-65 million strong today. Extended from Yemen, southern Saudi Arabia to United Arab Emirates, Oman and Qatar. But they may found in north Africa , Egypt and other countries after series of migration events.

• The second group is know as (Arab Musta’arbah: Adnan العرب المستعربة) means those who were not speaking Arabic originally but because of their contact to the original Arabs they start speaking Arabic. This happens thousands of years ago.

Those 2 groups of Arabs are distributed in 10-12 countries out of the 23 countries in the Arab league. The rest of Arab countries include the following ethnic groups who speak Arabic language but belong to mixed or different ethnic groups (see figure 1 and table 2):

• Egyptians (heavily mixed with the Arabs for the last 15 centuries).
• Berbers (or known today as Imazghien) distributed in 6 countries.
• African-Arab in Sudan, Somalian and Djibouti.

Table(1)

Figure(1)

Table (2)

Notes:

• Populations size reference is the CIA World Book
• The goal of this article is to give rough idea about the heterogeneity of Arab world populations and and should not to be used as a reference.
• Any input, correction, suggestions from our Arab colleagues about the above information will be much appreciated :)