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The scientific study of human evolution encompasses the development of the genus Homo, but usually involves studying other hominids and hominines as well, such as Australopithecus. "Modern humans" are defined as the Homo sapiens species, of which the only extant subspecies is known as Homo sapiens sapiens. Homo sapiens idaltu (roughly translated as "elder wise human"), the other known subspecies, is now extinct.[15] Homo neanderthalensis, which became extinct 30,000 years ago, has sometimes been classified as a subspecies, "Homo sapiens neanderthalensis"; genetic studies now suggest that the functional DNA of modern humans and Neanderthals diverged 500,000 years ago.[16] Similarly, the few specimens of Homo rhodesiensis have also occasionally been classified as a subspecies, but this is not widely accepted. Anatomically modern humans first appear in the fossil record in Africa about 195,000 years ago, and studies of molecular biology give evidence that the approximate time of divergence from the common ancestor of all modern human populations was 200,000 years ago.[17][18][19][20][21] The broad study of African genetic diversity headed by Dr. Sarah Tishkoff found the San people to express the greatest genetic diversity among the 113 distinct populations sampled, making them one of 14 "ancestral population clusters". The research also located the origin of modern human migration in south-western Africa, near the coastal border of Namibia and Angola.[22]

The evolutionary history of the primates can be traced back 65 million years, as one of the oldest of all surviving placental mammal groups. The oldest known primate-like mammal species, the Plesiadapis, come from North America, but they were widespread in Eurasia and Africa during the tropical conditions of the Paleocene and Eocene. Molecular evidence suggests that the last common ancestor between humans and the remaining great apes diverged between 8 and 4 million years ago, first the gorillas, and then the chimpanzees (genus Pan) split off from the line leading to the humans; the functional human DNA is approximately 98.4% identical to that of chimpanzees when comparing single nucleotide polymorphisms (see Human evolutionary genetics). The closest living relatives of humans are gorillas and chimpanzees, but humans did not evolve from these apes: instead they share a common ancestor with modern humans.[23]

Humans are probably most closely related to two chimpanzee species: Common Chimpanzee and Bonobo.[23] Full genome sequencing has resulted in the conclusion that "after 6.5 [million] years of separate evolution, the differences between chimpanzee and human are ten times greater than those between two unrelated people and ten times less than those between rats and mice".[attribution needed] Suggested concurrence between the functional human and chimpanzee DNA sequences range between 95% and 99%;[24][25][26][27] It has been estimated that the human lineage diverged from that of chimpanzees about five million years ago, and from that of gorillas about eight million years ago. However, a hominid skull discovered in Chad in 2001, classified as Sahelanthropus tchadensis, is approximately seven million years old, which may indicate an earlier divergence.[28]

Human evolution is characterised by a number of important morphological, developmental, physiological and behavioural changes, which have taken place since the split between the last common ancestor of humans and chimpanzees. The first major morphological change was the evolution of a bipedal locomotor adaptation from an arboreal or semi-arboreal one,[29] with all its attendant adaptations, such as a valgus knee, low intermembral index (long legs relative to the arms), and reduced upper-body strength.

Later, ancestral humans developed a much larger brain – typically 1,400 cm³ in modern humans, over twice the size of that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differs from that of other apes (heterochrony), and allows for extended periods of social learning and language acquisition in juvenile humans. Physical anthropologists[who?] argue that the differences between the structure of human brains and those of other apes are even more significant than their differences in size.

Other significant morphological changes included the evolution of a power and precision grip,[30] a reduced masticatory system, a reduction of the canine tooth, and the descent of the larynx and hyoid bone, making speech possible. An important physiological change in humans was the evolution of hidden oestrus, or concealed ovulation, which may have coincided with the evolution of important behavioural changes, such as pair bonding. Another significant behavioural change was the development of material culture, with human-made objects becoming increasingly common and diversified over time. The relationship between all these changes is the subject of ongoing debate.[31][32]

The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15,000 years.[33]

Uzay yahud fezâ, dünya'nın atmosferi dışında evrenin geri kalan kısmına verilen isimdir. Ortalama ısısı -270 santigrat derecedir. Atmosfer ile uzay arasında kesin bir sınır bulunmamaktadır, fakat Dünya'nın atmosferi yukarı doğru çıkıldıkça incelmektedir. Uzayda tahminen milyonlarca galaksi bulunmaktadır. Bu tahmini galaksilerin içinde tahminen milyonlarca sistemler, gezegenler ve astroitler bulunmaktadır. Fizikçi Carl Sagan'ın kitabı "KOZMOS" da yazdığı üzerine evrensel atom sabiti 1088 kadar yani 10 üssü 88, Carl Sagan'a göre evrende tahmini 10'un yanında 88 sıfır tane atom var (on oktovigintilyon). Bu şekilde bir hesaplama ve insanoğlunun bildiği her türlü galaksi uzayın büyüklüğünü kanıtlar.

Uzay karanlığı, büyüklüğü, olayları ile ilgi çekici, karmaşık ve araştırmaya değer olmuştur. Bu yüzden insan her çağda uzayı merak etmişti. Bu yüzden sürekli uzayı araştırmak için icatlar yapmıştı. Teleskop bu alanda çok önemli bir alettir. Çağlar geçtikçe insanların daha güçlü teleskoplarla uzayı incelemesi uzay hakkındaki bilgileri artırdı. Böylece merakını gidermeye başlayan insanoğlu bununla yetinmeyip uçarak daha fazla bilgi toplamak istedi. insanlığın uçmayı keşfetmesiyle Dünya'yı çevreleyen yakın uzay hakkındaki bilgiler, daha da artmaya başladı. Nihayet, güçlü füzeler, yapma uydular, Ay 'a insanlı ya da insansız araçlar gönderilmesi, yapay uydular geliştirilmesi, çok güçlü radyo teleskoplarla (bkz. Hubble Uzay Teleskobu) uzayın derinliklerinin araştırılması, 20. yüzyılın ikinci yarısında insanlığın uzay hakkındaki bilgilerini önemli ölçüde genişletti. Ayrıca insanlık uzayı araştırmak için "astronomi" bilimini doğurdu. Artık astrologlar uzayın bilgilerini daha hızlı buluyorlardı.

Bu arada teorik fizik ve astronomi konusunda devrim yapacak görüşler ortaya atan Einstein gibi bilginlerin uzay konusunda ortaya attıkları pek çok kuram, gözlemcilerin uzay üzerine verdikleri bulguların mantıklı bir şekilde açıklanmasını sağladı.

Uzay konusundaki ilk sağlam bilgiler, 19. yüzyıl sonu ile 20. yüzyıl başında, özellikle kuzey ülkelerinde kurulan gözlemevleri sayesinde alındı. ABD'nin Kaliforniya eyaletinde bulunan Palamar Gözlemevi, Dünya'da mevcut gözlemevlerinin en büyüğüdür. Buradaki aynalı teleskopun çapı 5 m, yüksekliği 40 metre dir.Bu gözlemevlerinde uzaydaki gökcisimlerinin kütlesi, hacmi, ışığının şiddeti vb. incelenmektedir. Uygulamalı fiziğin geliştirdiği tayf (spektrum) analizi, uzaydan gelen ışıklardan, cisimlerin hangi elementlerden oluştuğunu göstermektedir.

1932'de K. G. Jansky adındaki bir mühendisin rastlantı sonucu bulduğu uzaydan gelen radyo yayınları, daha sonraki yıllarda radyoteleskopların doğmasına ve uzayın derinliklerinin dinlenmesine, bu radyo yayınlarının kaynaklarının ve nedenlerinin bulunmasına yol açtı. II. Dünya Savaşı sırasında Almanların geliştirdiği V-1 ve V-2 füzeleri daha sonraki yıllarda uzayın keşfi için yapılacak çalışmalarda büyük bir adım oldu. 1947-1956 yılları arasında özellikle ABD, uzay çalışmalarına büyük hız verdi. Yapılan uzay uçuşu denemelerinin hiçbiri bir uzay aracını yörüngeye oturtmayı başaramadı. Bu arada SSCB, 1957 yılında üç kademeli Vostok füzeleri ile "Sputnik" adındaki ilk yapma uyduyu Dünya çevresinde yörüngeye oturtarak uzay yarışında öne geçti. Uydulardan elde edilen uzay üzerine bilgiler, canlıların, özellikle insanların uzayda yaşayabilmeleri için hangi koşulların yerine getirilmesi gerektiğini ortaya koydu. Böylece uzay tıbbı doğdu ve gelişti. Uzayda ilk insan ise 12 Nisan 1961 tarihinde SSCB'nin uzaya gönderdiği Yuri Gagarin oldu. Bu arada, insanların uzay boşluğuna yerleşmelerini sağlamak, uzayı uzaydan izlemek, Dünya üzerinde haberleşme kolaylıkları sağlamak için binlerce uydu yörüngeye yerleştirildi ya da uzayın boşluğuna fırlatıldı. Nihayet 1969 Temmuzu'nda Ay'ın ABDli astronotlar tarafından fethedilmesi, uzay çalışmalarında en önemi adımlardan biri oldu. Günümüzde uzay yarışı büyük bir hızla sürmektedir.Özellikle de Amerika ve Rusya bu büyük yarışta amansız birer rakiptir.

Uzay Hakkındaki bir başka teorem ise 2009'da öne sürülmüştür. Buna göre Uzay tahmin edilenden daha küçük olabilir. Galaksi sayısı ise tahmin edilenden çok daha azdır. Görünen uzayda görülen galaksilerin ve yıldızların pek çoğu aynı galaksilerin farklı zamanlardaki görüntüleridir. Işık uzayda doğrusal ilerlemez, evrensel çekim güçlerinin belirlediği yolu takip eder, kim bilir yeterince uzun süre uzayı gözlemlersek belki bir gün kendimizi bile görebiliriz.

Kristol was key to the defeat of the Clinton health care plan in 1993. In the first of what would become legendary strategy memos circulated among Republican policymakers, Kristol said the party should "kill," not amend, President Clinton's health care plan. Kristol's memo immediately united Republicans behind total opposition to Clinton's reform plan. A later memo advocated the phrase, "There is no health care crisis," which Senate Minority Leader Bob Dole used in his response to Clinton's 1994 State of the Union address.

Kristol was a leading proponent of the Iraq War. In 1998, he and other prominent foreign policy experts sent a letter to President Clinton urging a stronger posture against Iraq. Kristol argued that Saddam Hussein posed a grave threat to the United States and its allies: "The only acceptable strategy is one that eliminates the possibility that Iraq will be able to use or threaten to use weapons of mass destruction. In the near term, this means a willingness to undertake military action as diplomacy is clearly failing. In the long term, it means removing Saddam Hussein and his regime from power. That now needs to become the aim of American foreign policy.".[6]

In the 2000 Presidential election, Kristol was a supporter of John McCain. In response to a question from a PBS reporter about the Republican primaries, he stated, "No. I had nothing against Governor Bush. I was inclined to prefer McCain. The reason I was inclined to prefer McCain was his leadership on foreign policy.".[7]

After the Bush administration developed its response to September 11th, 2001, Kristol said, "We've just been present at a very unusual moment, the creation of a new American foreign policy." [7] Kristol ardently supported the Bush administration's decision to go to war with Iraq. In 2003, he and Lawrence Kaplan wrote The War Over Iraq, in which he described the reasons for removing Saddam.

As the military situation in Iraq began to deteriorate in 2004, Kristol argued for an increase in the number of U.S. troops in Iraq. In 2004, he wrote an op-ed strongly criticizing Secretary of Defense Donald Rumsfeld, saying he "breezily dodged responsibility" for planning mistakes made in the Iraq War, including insufficient troop levels.[8] In September 2006, he wrote, with fellow commentator Rich Lowry, "There is no mystery as to what can make the crucial difference in the battle of Baghdad: American troops."[9]

This was one of the early calls for what became the Iraq War troop surge of 2007 four months later. In December 2008, Kristol wrote that the surge was "opposed at the time by the huge majority of foreign policy experts, pundits and pontificators," but that "most of them — and the man most of them are happy won the election, Barack Obama — now acknowledge the surge’s success."[10]

Kristol was one of many conservatives to publicly oppose Bush's second U.S. Supreme Court nominee, Harriet Miers. He said of Miers: "I'm disappointed, depressed, and demoralized. [... ] It is very hard to avoid the conclusion that President Bush flinched from a fight on constitutional philosophy. Miers is undoubtedly a decent and competent person. But her selection will unavoidably be judged as reflecting a combination of cronyism and capitulation on the part of the president."

He was a vocal supporter of the 2006 Lebanon War, stating that the war is "our war too," referring to the United States.

Kristol was an ardent promoter of Sarah Palin, advocating for her selection as the running mate of John McCain in the 2008 U.S. Presidential Election months before McCain chose her.[11][12]

In response to Iran's nuclear program, Kristol supports the strong sanctions. In June 2006, at the height of the Lebanon War, he suggested that, "We might consider countering this act of Iranian aggression with a military strike against Iranian nuclear facilities. Why wait?"[13]

In 2010, Kristol criticized the Obama administration and Joint Chiefs of Staff Chairman Admiral Mike Mullen for an unserious approach to Iran. He wrote, "The real question is what form of instability would be more dangerous--that caused by this Iranian regime with nuclear weapons, or that caused by attacking this regime's nuclear weapons program. It's time to have a serious debate about the choice between these two kinds of destabilization, instead of just refusing to confront the choice."[14]